Arxiu de la categoria: Terrestrial mammals

The most recent extinct mammals because of humans

The history of life is full of extinctions of living beings, some massive and popularly known, such the one that extinguished dinosaurs. Extinction is a usual process, perhaps necessary, in biological evolution. Even so, the responsibility of the human species for the high rate of extinctions in recent years is alarming. We can even talk of a new geological era, in which the planet globally is changing due to our activity: the Anthropocene. In this post you will meet four mammals that existed only 300 years ago and we will never see alive again. Or maybe will we recover them back from extinction?

THE MOST RECENT EXTINCT MAMMALS BECAUSE OF HUMANS

1. THE THYLACINE

Thylacine, Tasmanian wolf or Tasmanian tiger. Despite its many names, the thylacine (Thylacinus cynocephalus) was not related to wolves or tigers (placental mammals), as it was a marsupial animal, like kangaroos and koalas.

One of the few thylacines that are preserved taxidermized in the world. Museo nacional de Ciencias Naturales, Madrid. Photo: Mireia Querol Rovira

The thylacine was a solitary and twilight hunter, who caught his prey by ambush, since it was not very fast. A unique feature was the ability he had to open his mouth: the powerful jaws could open at an angle of 120 degrees. Watch it in the following video:

In the same way as the rest of the marsupials, the offspring were not born directly, but instead developed in the marsupium (popularly known as the mother’s “bag”).

Extinction and protection of the thylacin

The last known wild specimen was hunted in 1930, and in 1933 the last captive specimen in a zoo died, 125 years after its description (1808). There are several hypotheses about its extinction:

  • Intensive hunting: As with the wolf in Spain nowadays, the thylacine was accused of killing cattle, so rewards were offered for dejected animals. Subsequent studies have concluded that their jaw was not strong enough to kill an adult sheep.
  • Reduction of habitat and prey: with the colonization of Australia, their habitats and habitual preys were reduced.
  • Introduction of invasive species and diseases: colonization also led to the introduction of species that competed with the thylacine (dogs, foxes…) and new diseases to which it was not immunized.

The protection of the species was approved 59 days before the death of the last individual. The law was clearly late and insufficient.

If you want to know more about the thylacine, we encourage you to read The thylacine: we extinguished it.

2. THE QUAGGA

The quagga (Equus quagga quagga) it was a subspecies of zebra that inhabited the plains of South Africa. The anterior half of the body had the typical black and white stripes of the zebra. The stripes blurred to give rise to a brownish color on its back, so it was initially believed to be a separate species from the common zebra (Equus quagga). The legs were white.

Its strange name belongs to the onomatopoeia, in the language of the Khoi, of the noise that quaggas made.

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Taxidermized quagga in the Museum of Natural History of Bamberg. There are only 23 quaggas dissected worldwide. Photo: Reinhold Möller

Extinction and recovery of the quagga

The last wild specimen died in 1870, and the last one in captivity died in 1883 at the Amsterdam zoo, only 98 years after its description (1785). Although the quagga began to be hunted by Dutch settlers to use their flesh and skin, the decline in population was accelerated until extinction because of the intensive hunting to exterminate wild animals in the area, and thus use the pastures for domestic cattle.

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Of the few existing photographs of a quagga, at the London Zoo (1870). Photo: Biodiversity Heritage Library (public domain)

At the time no conservation effort was made. Moreover, it was not known that the quagga of the Amsterdam zoo was the last one. However, quagga has the dubious honor of being the only extinct species that has “come back to life” thanks to a project called The Quagga Project, which began in 1987.

When it was discovered that the quagga was not a separate species from the zebra, but a subspecies, its DNA was sequenced and compared with zebra’s DNA. After all, if they were subspecies, zebras had to have quaggas’ DNA in their genes. By selective breeding of zebras with a tendency to disappearing stripes, some quaggas are currently grazing in fields of northern South Africa.

Although the first technique that is intended for the recovery of extinct species is cloning, in the case of quaggas it has been possible through the reproduction of selected zebras, thanks to the quagga DNA preserved in its genome, even if they are not 100% quaggas identical to their extinct ancestors.

In this video you can see current quaggas and the investigation process followed to “resuscitate them” (english subtitles):

3. STELLER’S SEA COW

Steller’s sea cow (Hydrodamalis gigas) was a sirenium, that is, a marine mammal of the same order as manatees and dugong. It was distributed by the Bering Sea, near Kamchatka (Eastern Russia). It was up to 8 meters long and weighed 5 tons.

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Model and skeleton of Steller’s sea cow. Photo: KKPCW

Unlike the rest of the sirenians, who live in the Indian Ocean and part of the Pacific, Steller’s sea cow lived in cold waters, had fewer teeth and was the best sirenium adapted to marine life. It was totally herbivorous (algae and plants).

Extinction and conservation of Steller’s sea cow

Steller’s sea cow has the sad record of being the fastest animal to become extinct since its discovery in 1741: only 27 years. The cause is, again, indiscriminate hunting by seal hunters and whalers, to take profit from the skin, meat, and fat. With hardly any predators, sea cows were easy prey. No effort was made to conserve the species.

Currently, there are only about 20 skeletons and few skin samples.

4. WESTERN BLACK RHINOCEROS

We finish the list of recently extinct mammals with the western black rhinoceros (Diceros bicornis longipes), a subspecies of the black rhinoceros. It was almost 4 meters long and could weigh up to 1.3 tons. Like all rhinos, they were herbivores.

rinoceronte negro occidental, wester black rino, rinoceront negre
Western black rhino. Source: savetherhino.org

Extinction and conservation of the western black rhinoceros

He lived in the savanna of central-western Africa only 8 years ago (IUCN declared it extinct in 2011). The causes of its extinction were:

  • Habitat loss.
  • Slaughtering by farmers to protect their crops.
  • And especially poaching, mainly to market with their horns and as hunting trophies. Rhinoceros horns are used in traditional Chinese medicine without any scientific evidence. If you want to know more animals threatened due to this activity, you can read The five most threatened species by traditional Chinese medicine.

There were 850,000 individuals registered at the beginning of the 20th century. Between 1960 and 1995, poachers reduced its population by 98%. In 2001, there were only 5 live rhinos left. In spite of the conservation measures taken at the beginning of the 20th century, the fight against hunting and enforcement of judgments against the poachers were declining over time, which led to the disappearance of the subspecies.

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Rhinoceros with their amputated horn. Foto: A. Steirn

Another subspecies of rhinoceros has become extinct in recent years: the southern black rhinoceros (Diceros bicornis bicornis) disappeared in 1850 due to excessive hunting and habitat destruction. The rest of the subspecies are critically endangered.

TO THINK ABOUT

The list of extinct animals in historical times and because of human action does not stop growing. Some species such as the Chinese river dolphin or Baiji (Lipotes vexillifer), have been declared extinct on more than one occasion. IUCN currently has it categorized as critically endangered-possibly extinct, although there is no solid evidence of its existence since 2007. The vaquita porpoise (Phocoena sinus) can be the next, with only 12 specimens detected in 2018.

baiji, delfin de rio chino, river dolphin, China, extinct, extinto extingit
This Baji was photographed before his death in captivity, 2002. Photo: Institute of Hydrobiology, Wuhan, China

Although animals, and especially mammals, include the most iconic species that the popular opinion wants to conserve, we must not forget the biological value of other species of animals, plants, fungi, algae and even bacteria, from which we should avoid their extinction. In a future post, we will write about some of these species.

Animals walking on walls: challenging gravity

How do insects, spiders or lizards for walking on smooth vertical surfaces or upside down? Why would not be possible for Spiderman to stick on walls the way some animals do?

Scientist from several areas are still in search of the exact mechanisms that allow some animals to walk on smooth surfaces without falling or sliding. Here we bring you the latest discoveries about this topic.

Animals walking on walls: challenging gravity

Competition for space and resources (ecological niche) has led to a lot of amazing adaptations throughout the evolution of life on Earth, like miniaturization.

When nails, claws or friction forces are insufficient to climb up vertical smooth surfaces, dynamic adhesion mechanisms come into play. Dynamic adhesion mechanisms are defined as those that allow some animals to climb steep or overhanging smooth surfaces, or even to walk upside down (e.g. on ceilings), by attaching and detaching easily from them. The rising of adhesive structures like adhesive pads as an evolutionary novelty has allowed some animals to take advantage of unexplored habitats and resources, foraging and hiding from predators where others could not.

Gecko stuck on a glass surface. Picture by Shutterstock/Papa Bravo.

Adhesive pads are found in insects and spiders, some reptiles like geckos and lizards, and some amphibians like tree frogs. More rarely they can be also found in small mammals, like bats and possums, arboreal marsupials native to Australia and some regions from the Southeast Asia.

The appearance of adhesive pads among these very different groups of animals is the result of a convergent evolution process: evolution gives room to equal or very similar solutions (adhesive pads) to face the same problem (competence for space and resources, high predation pressure, etc.).

Adaptation limits (or why Spiderman could not climb up walls)

Studying the underlying processes of the climbing ability of these animals is a key point in the development of stronger adhesive substances. So, a lot of research regarding this topic has been carried out to date.

Will humans be able to climb up walls like Spiderman some day? Labonte et al. (2016) explain us why Spiderman could not be real. Or, at least, how he should be to be able to stick on walls and do whatever a spider can.

Will humans be able to climb up walls like Spiderman some day? For now, we will have to settle for this sculpture. Public domain image.

Apart from the specific mechanisms of each organism (of which we will talk in depth later), the main principle that leads the ability for walking on vertical smooth surfaces is the surface/volume ratio: the smaller the animal, the larger is the total surface of the body with respect its volume and smaller is the amount of adhesive surface needed to avoid falling due to the body weight. According to this, geckos are the bigger known animals (i.e. those with the smallest surface/volume ratio) able to walk on vertical smooth surfaces or upside down without undergoing deep anatomical modifications.

And what does ‘without undergoing deep anatomical modifications’ mean? The same authors say that the larger the animal, the bigger is the adhesive pad surface needed for walking without falling to the ground. The growth of the adhesive pad surface with respect the size of the animal shows an extreme positive allometry pattern: by a small increase of the animal size, a bigger increase of the adhesive pad surface takes place. According to this study, a 200-fold increase of relative pad area from mites to geckos has been observed.

Picture by David Labonte

However, allometry is led by anatomical constraints. Therefore, if there was an animal larger than a gecko able to climb up smooth surfaces, it should have, for example, extremely large paws covered by an extremely large sticky surface. While this would be possible from a physical point of view, anatomical constraints would prevent the existence of animals with such traits.

Now we are in condition to answer the question ‘Why Spiderman could not stick to walls?’. According to Labonte et al., to support a human’s body weight, an unrealistic 40% of the body surface would have to be covered with adhesive pads (80% if we only consider the front of the body) or ridiculously large arms and legs should be developed. Both solutions are unfeasible from an anatomical point of view.

Great diversity of strategies

Dynamic adhesion must be strong enough to avoid falling as well as weak enough to enable the animal to move.

A great diversity of dynamic adhesion strategies has been studied. Let’s see some of the most well-known:

Diversity of adhesive pads. Picture by David Labonte.

1) Wet adhesion

A liquid substance comes into play.

Insects

Insects develop two main mechanisms of wet adhesion:

Smooth adhesive pads: this mechanism is found in ants, bees, cockroaches and grasshoppers, for example. The last segment of their legs (pretarsus), their claws or their tibiae present one or several soft and extremely deformable pads (like the arolia located in the pretarsus). No surface is completely smooth at microscale, so these pads conform to the shape of surface irregularities thanks to their softness.

Cockroach tarsus. Adapted picture from the original by Clemente & Federle, 2008.

Hairy adhesive pads: these structures are found in beetles and flies, among others. These pads are covered by a dense layer of hair-like structures, the setae, which increase the surface of the leg in contact with the surface.

Chrysomelidae beetle paw. Picture by Stanislav Gorb et al.

A thin layer of fluid consisting of a hydrophilic and a hydrophobic phase located between the pad and substrate comes into play in both strategies. Studies carried out with ants show that the ends of their legs secrete a thin layer of liquid that increases the contact between the pretarsus and the surface, filling the remaining gaps and acting as an adhesive under both capillarity (surface tension) and viscosity principles.

Want to learn more about this mechanism in insects? Then do not miss the following video about ants!

Tree frogs

Arboreal or tree frog smooth toe pads are made of columnar epithelial cells separated from each other at their apices. Mucous glands open between them and secrete a mucous substance that fill the intercellular spaces. Having the cells separated enable the pad to conform to the shape of the surface and channels that surround each epithelial cell allow to spread mucus over the pad surface to guarantee the adhesion. These channels also allow to remove surplus water under wet conditions that could make frogs to slide (most tree frogs live in rainforests).

Red-eyed tree frog (Agalychnis callidryas), distributed from Southern Mexico to Northeastern Colombia. Public domain image.

In the next video, you can see in detail the legs of one of the most popular tree frogs:

Smooth toe pads of tree frogs are similar to those found in insects. In fact, crickets have a hexagonal microstructure reminiscent of the toe pads of tree frogs. This led Barnes (2007) to consider the wet adhesion mechanism as one of the most successful adhesion strategies.

Different species of tree frogs (a, b, c) and their respective epithelia (d, e, f). Figure g corresponds to the surface of a cricket’s smooth toe pad. Picture by Barnes (2007).

Possums

The most detailed studies on possums have been carried out about the feathertail glider (Acrobates pygmaeus), a mouse-sized marsupial capable to climb up sheets of glass using their large toe pads. These pads are conformed by multiple layers of squamous epithelium with alternated ridges and grooves that allow them to conform to the shape of the surface and that are filled with sweat, the liquid this small mammal use to adhere to surfaces.

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Acrobates pygmaeus. Picture by Roland Seitre.
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Frontal toe pads of Acrobates pygmaeus. Picture by Simon Hinkley and Ken Walker.

2) Dry adhesion

Liquid substances do not come into play.

Spiders and geckos

The adhesion of both spiders and geckos depends on the same principle: the Van der Waals forces. Unlike insects, tree frogs and possums, these organisms do not secrete sticky substances.

Van der Waals forces are distance-dependent interactions between atoms or molecules that are not a result of any chemical electronic bond. These interactions show up between setae from footpads of geckos (which are covered by folds, the lamellae) and setae from spider paws (which are covered with dense tufts of hair, the scopulae), and the surface they walk on.

Spider paw covered with setae. Picture by Michael Pankratz.
Diversity of footpads of geckos. Picture by Kellar Autumn.

However, recent studies suggest dry adhesion in geckos is not mainly lead by Van der Waals forces, but by electrostatic interactions (different polarity between setae and surface), after confirming that their sticking capacity decreased when trying to climb a sheet of low energetic material, like teflon.

Anyway, the ability of geckos to climb is impressive. Check this video of the great David Attenborough:

3) Suction

Bats

Disk-winged bats (family Thyropteridae), native to Central America and northern South America, have disk-shaped suction pads located at the base of their thumbs and on the sole of their feet that allow them to climb smooth surfaces. Inside these disks, the internal pressure is reduced, and the bat stick to the surface by suction. In fact, a single disk can support the weight of the bat’s body.

Thyropteridae bat. Picture by Christian Ziegler/ Minden Pictures.

Now that you know about all these animals’ ability for climbing smooth walls, do you still think Spiderman is up to the task?

Main picture by unknown author. Source: link.

The problem of wild animals as pets

Although the first animals we think of as life partners are dogs or cats, the truth is that unfortunately many people decide to have a wild or exotic animal at home. Vietnamese pot-bellied pigs, sugar gliders, fennec foxes, meerkats, raccoons, monkeys… Is it possible to have a wild animal in good condition at home? What are the issues we can find? What wild mammals do people have as pets? We invite you to continue reading to find out.

WHAT IS THE DIFFERENCE BETWEEN A DOMESTIC ANIMAL AND A WILD ONE?

A domestic animal is an animal that has lived with humans for thousands of years. During the history of our species we have artificially selected these animals to obtain benefits, such as food, companionship or protection, like dogs, which have even co-evolved with us. Most domestic animals could not survive in the wild, as they would not know how to find food or would be easy prey for predators. Those who survive when abandoned, like some dogs or cats, cause serious problems to wildlife or even people.

 lobo perro dog wolf perro lobo
Some domestic animals, such as certain dog breeds (right), resemble their wild counterparts (wolf, left), which gives rise to the false idea that wild animals can be domesticated. Photo: unknown

And a wild animal? Many people confuse wild animal with ferocious or dangerous animal. A wild animal is an animal that has not been domesticated, that is, its species has not been in contact with people (at least not for thousands of years as the domestic ones). The fact that some wild animals are not dangerous (or not at all) for us, that they appear in series and movies, some celebrities own them and the desire to have a “special” animal at home, continues favoring the purchase-sale of these animals as pets.

monkey mono capuchino marcel ross friends
The character of Ross in the world-famous series ‘Friends’ had a capuchin monkey, which has to be donated when it reaches sexual maturity for aggressive behavior. Source

WHAT PROBLEMS DOES IMPLY TO HAVE A WILD ANIMAL AT HOME?

PROBLEMS FOR PEOPLE

The main reason why wild or exotic animals cause problems for humans is the lack of knowledge of the species: some have very specific diets that are practically impossible to reproduce in captivity. Others may live longer than the owner, be very noisy, occupy a lot of space, have nocturnal habits, transmit diseases or be poisonous. This results in maintenance difficulties and changes in  the behavior of the animal, until it becomes dangerous for its owner. The consequence is usually the abandonment of the animal, which will cause death, cause problems in nature or very high maintenance costs if they end up in a wildlife rescue center (according to Fundació Mona, keeping a chimpanzee costs 7,000 euros a year. Their life expectancy is 60 years: 420,000 euros in total for a single animal).

Raccoons undergo behavioral changes and may attack their owners. Source

Many species released in the wild end up being invasive, endangering the native ecosystems. If you want to know the difference between introduced and invasive species, read this post. To know the threats they pose to ecosystems, visit this post.

Do not forget that the purchase, sale and possession of many wild animals is totally illegal.

PROBLEMS FOR ANIMALS

Animals must live in an environment where their needs, both physical and mental, can be met. Although we put all our good intentions, give love and spend money keeping a wild animal, we  will never be able to reproduce their natural conditions. Lack of space, contact with other animals of their species, time searching for food, temperature conditions, humidity, light… the animal can not develop its normal behavior even if it is in the most optimal conditions of captivity.

The consequences that will suffer an animal that has not met their needs implies health problems (diseases, growth deficit…) and behavior (stereotypic-compulsive movements, self-injury, anxiety, aggression…).

A fennec fox, a carnivorous animal of the desert, in an evident state of illness. According to social networks, because he was being fed a vegan diet. According to its owner, Sonia Sae, because it is allergic to pollen despite following a vegan diet. Be that as it may, it is clear that the pollen amounts in Sahara have nothing to do with those of Europe. Source

Finally, the most serious consequence when we acquire a wild animal is that we are favoring the trafficking of animals, the death of thousands of them during transport to our house and even their extinction. Animal trafficking is the second cause of biodiversity loss on our planet, behind the destruction of habitats.

Slow loris are nocturnal and poisonous animals that are marketed as pets and, like mostof them, are transported under terrible conditions. Learn more about the calvary of slow lories visiting blognasua. Photo: Naturama

EXAMPLES OF WILD MAMMALS AS PETS

PRIMATES

Marmosets, slow loris, lar gibbons, chimpanzees, Barbary macaques… The list of primates that people have in captivity is almost infinite. One of the main mistakes people make when they want a primate as a pet is to believe that they have our same needs, especially in superior primates such as chimpanzees. Its expressions are also confused with ours: what the photo shows is not a smile of happiness and what the video shows is not tickling, but an attitude of defense (slow loris have poison in their elbows).

This chimpanzee is not smiling, he is scared. Photo: Photos.com

Many primates live in family groups and the offspring need to be with the mother the first years of life, so that just the simple fact of acquiring a little primate entails the death of all the adults of their family group and psychological problems for the animal. To know the extensive and serious problem of keeping primates in captivity, we strongly recommend reading this post.

SUGAR GLIDERS

Sugar gliders (Petaurus breviceps) resemble a squirrel, but in fact they are marsupials. They have a very specific diet (insects and their depositions, eucalyptus sap, nectar …), they live in the canopy of trees in groups from 6 to 10 individuals and move between the trees jumping up to 50 meters with a membrane that let them hover. They are nocturnal so they yell and call at night. It is evident that it is impossible to reproduce these conditions in captivity, so the majority of sugar gliders die due to nutritional deficiencies.

Sugar glider caged. Photo: FAADA

VIETNAMESE POT-BELLIED PIGS

Although they are a variety of a domestic animal, Vietnamese pot-bellied pigs (Sus scrofa domestica) are small when tey are young, but adults can weigh more than 100 kilos, so it is impossible to keep them in a flat. There have been so many abandonments and they have reproduced so much, that there are populations established in nature. They can reproduce with wild boars and it is unknown if the hybrids are fertile. There are no wildlife recovery centers or shelters for these pigs, so they continue to affect the native ecosystems.

Since actor George Clooney introduced a Vietnamese pot-bellied pig as a pet, the trend to own one quickly spread. Source

RACCOONS AND COATIS

Other mammals that, because of their pleasant appearance, some people try to have as pets. Raccoons (Procyon sp) develop aggressive behaviors when they do not having their needs covered, they are destructive to household objects and have a tendency to bite everything, including people. Currently in Spain and other countries it is illegal to acquire them and it is classified as an invasive species.

In addition to aggressiveness, one of the most common behaviors of raccoons is “theft”. Source

Coatis (Nasua sp) are related to raccoons and, like them, when they grow up they become aggressive if kept in captivity in a home. In Spain, their possession is also illegal.

coatí nasua
The coati, another friendly-looking mammal that can be dangerous. Source

MERKAATS

Merkaats (Suricata suricatta) are very social animals that live in colonies of up to 30 individuals underground in the South African savanna. They usually make holes in the ground to protect themselves and are very territorial. Therefore, having a meerkat at home or in a garden is totally unfeasible. In addition, the climatic conditions (high temperatures and low humidity) in which they are adapted are not the same as those of a private home.

As sugar gliders, their food is impossible to reproduce at home: snake meat, spiders, scorpions, insects, birds and small mammals… Like raccoons, they do not hesitate to bite and are very active animals.

Meerkat with a leash where you can see his fangs. Photo: FAADA

FENNEC FOX

This species of desert fox (Vulpes zerda) has also become trendy as a pet. Although its tenure is still legal, it has been proposed several times as an invasive species.

The main reason why you can not have a fennec at home are the desert climatic conditions to which it is adapted. Living in an apartment causes kidney problems and thermoregulation problems. Also, it is a nocturnal animal. Changes in their circadian rhythm cause them hormonal problems.

Fennec  fox in the desert. Photo: Cat Downie / Shutterstock

Like the previous two species, behavioral problems can turn up and become violent against the furniture or its owners.

ELEPHANTS, TIGERS …

Although it may seem incredible, there are people who have an elephant in the home garden and other people have felines, like tigers. At this point we do not think it is necessary to explain the reasons why these animals have not their needs met and the potential danger they pose to their owners and neighbors in case of escape.

Dumba, the elephant that lives in a home garden in Spain. Photo: FAADA

IN CONCLUSION

As we have seen, a wild animal in captivity will never have its needs covered to guarantee its welfare. Here we have presented the best known wild mammals that are kept as pets, but unfortunately the list does not stop expanding.

In order not to favor animal trafficking and cause unnecessary suffering during the life of the animal, avoid buying wild animals, inform yourself and inform the people around you, denounce irresponsible tenures and in case you already have one wild animal as a pet and you can no longer keep it, contact a recovery wildlife center and never abandon it into nature.

MIREIA QUEROL ALL YOU NEED IS BIOLOGY

 

Why sloths are so slow?

Sloths draw our attention with their cute appearance and for being the slowest mammals in the world. They also have green hair and claws like in a horror movie. Do you dare to find out more?

WHO ARE SLOTHS?

Sloths are animals of arboreal habits (they inhabit the humid forests of Central and South America). This could make us think that they are primates. Actually, they belong to a very different group, the same order where we classify anteaters and tamanduas (Order Pilosa). They are also relatives (although a little more remote) of armadillos. The six species that exist nowadays are classified as two-toed sloths and three-toed sloths, although many extinct species are known (some of them giant).

Three-toed sloth (Bradypus variegatus). Photo: Stefan Laube

They have legs with hook-like claws that allow them to hang perfectly from the branches, but on the ground they crawl awkwardly with the claws of the front legs, which are stronger. The three-toed sloth is also a good swimmer.

Unlike anteaters and tamanduas, they have a rounded face and no front teeth. The back teeth work as a shredder and grow continuously.

They have solitary habits.

Two-toed sloth (Choloepus hoffmanni). Photo: Masteraah

AN ALMOST PERFECT CAMOUFLAGE

Sloths have a thick and rough fur, with colors ranging from grayish brown to dark brown, black and even whitish. These colors, added to the slowness of their movements, allows them to go unnoticed. In case of danger, they stay still and if they are discovered by their predators, they will punch with the big claws.

In spite of everything, the fur of sloths can have a greenish color, due to the algae that grows between the hairs. The outer fur is also home to animals such as ticks, mites, beetles and even moths.

green sloth, peresós verd
Sloth with its green fur due to the algae that grow in it. Photo: unknowkn

REPRODUCTION

After mating, the gestation of sloths lasts 5-6 months. A single baby will be born, which hangs from the belly of its mother thanks to its well-formed claws. It will nurse for a month, after this time he will remain attached to the mother to learn the feeding patterns.

 

Mother sloth and baby. Photo: John Martin

FEEDING

Unlike their relatives, who mainly feed on insects such as ants or termites, sloths are folivores or phyllophags: they feed on leaves and buds of trees (especially from Cecropia). Some species complete their diet with insects and the algae of their fur.

Three-toed sloth (Bradypus variegatus) eating. Photo: Christian Mehlführer

They move very slowly through the trees with their hook-shaped claws as they feed. Living in the trees is also a good strategy to avoid their predators (anacondas, harpy eagles, pumas and jaguars, humans …).

In addition to this slowness, their muscles are small and weak for their body size (they have 30% less muscle mass than other mammals of their size). Its metabolism is also extremely slow compared to other mammals. As a result its body temperature is low (about 30° C). Three-toed sloths have the slowest metabolism of all mammals. Two-toed sloths are in the third place, after the panda.

WHY ARE THEY SO SLOW?

Take a loot at this video to see how slow are sloths:

Sloths are so slow that it would take them five minutes to cross a standard-widthstreet. Because their food is almost exclusively leaves, the energy they get from them is very scarce. Leaves have little energy and besides, it is very difficult to extract this energy. As we all know, the same amount of meat would give more energy. Other herbivorous animals supplement their vegetable diet with nuts or fruit, which give an extra boost of energy, but sloths don’t do this.

To counteract this drawback, sloths have two main adaptations:

  • A very large stomach (one third of their body) with several chambers to extract the maximum energy from leaves. This leads to digestions of five or seven days, even weeks.
  • Minimum use of energy, which it means not moving very much and using little energy to maintain their body temperature. To feed without spending a lot of energy, they live almost permanently in the trees and only go down to the ground once a week, to defecate or change to another tree (if they cannot change by the branches to the next tree). They spend most of their time eating, resting or sleeping.

ECOLOGICAL IMPORTANCE

Sloths are great seed dispersers and they fertilize the soil with their excrements.

As mentioned before, algae and moths, among other living beings, live in the fur of sloths. The symbiotic relationship they establish is fascinating. Sloths only come down from the trees once a week to defecate. At that time, moths deposit their eggs in the sloth’s stool. The moth larvae will feed on the feces. Once adult, moths fly to the sloth’s fur, where they will live and mate. Dead moths will be decomposed by fungi that live in the fur, and will transform them into ammonium, phosphates and nitrates that will help the algae to grow. It is believed that sloths complement their diet with these algae, rich in biolipids and other nutrients.

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Symbiotic relationship of sloths, algae, fungi and moths (click to enlarge). Source: see image

Besides, the species of micro and macroorganisms that live in their fur have substances against bacteria, cancer cells and parasites such as Plasmodium, responsible for malaria and Trypanosoma, responsible for Chagas disease.

CONSERVATION STATUS

Of the six known species, according to the IUCN Red List, three-toed sloths Bradypus pygmaeus and Bradypus torquatus are respectively critically endangered and vulnerable. The rest are least concern. As usual, habitat destruction is the main threat that sloths face today. Due to their slowness, they are quickly affected by the destruction of the forests that the urban advance entails or they are run over when trying to cross the roads.

green sloth, perezoso verde, peresós cerd, carretera, road, crossing, cruzando
Sloth crossing a road. Photo: Ian D. Keating

Even though they are completely harmless, some people also attack or kill them thinking they are dangerous.

Unfortunately, its friendly face and docile appearance has led to some people to have them as pets. We will never be tired of saying it: wild animals are not pets. Outside of their habitat their physical, nutritional or psychological needs can not be fulfilled. In addition, their extraction from nature is traumatic (they usually kill the mother to capture the young) and transport and storage occur in unhealthy conditions.

Caged sloth. Photo: unknown.

Protection of its habitat and laws in favor of sloths are priority conservation actions, in addition to the existence of rescue centers for injured or orphaned sloths.

Rescued orphan sloth. Phto: Becca Field

WHAT CAN YOU DO YOU?

Education is the most important cornerstone to start respecting nature. Tell the people around you about the unique characteristics of these animals, explain that they are not dangerous to avoid aggressions towards them and make them understand the suffering that involves having them pets. If you live in an area where there are sloths, call the authorities if you see any sloth in danger, trying to cross the road, for example.

If you want to delve into the topic, you can visit the TED-Ed lesson about sloths, the inspiration of this post.

MIREIA QUEROL ALL YOU NEED IS BIOLOGY

Cover image: Getty

Discovered a new species of orangutan on the verge of extinction

A few days ago the discovery of a new species of orangutan was announced. Unfortunately, it is critically endangered. How is it possible that it has not been discovered until now? What other species of orangutans exist? What threats do they face? Can we do something to protect them? Keep reading to fin d out!

KNOWING THE ORANGUTANS

We know a lot about orangutans because of the work of Biruté Galdikas, the biggest expert in behavior of orangutans, as well as Jane Goodall is from chimpanzees and Dian Fossey was from the mountain gorillas. The orangutan is an hominid, from the same family as humans, gorillas, chimpanzees and bonobos.

Orangutans are the most distant hominids from us. Despite this, we share 97% of the DNA and the oldest ancestor between orangutans and humans lived about 14 million years ago. If you want to learn more about who the hominids are and how primates are classified, you can read this post.

Until now, two orangutan species were known: the Sumatran orangutan (Pongo abelii) and the Bornean orangutan (Pongo pygmaeus). A recent research  from November 2017 adds a new species: the Tapanuli orangutan (Pongo tapanuilensis). Since 1929 a new species of great ape had not been discovered, despite being one of the most studied groups in the world.

Bornean, Sumatran and Tapanuli male orangutans. Photo: Eric Kilby Aiwok Tim Laman 

MORPHOLOGY

The orangutan (from the Malay orang hután, ‘person from the forest’) is distinguished from the other hominids by its orange fur. It feeds, sleeps and reproduces in the trees, although it occasionally goes down to the ground to drink from the rivers. Its long arms (up to 2.2 m) and prehensile feet are perfectly adapted to the arboreal life. The flexibility of the hip and other joints allows them to adopt impossible positions for other primates.

Sumatran female orangutan with her baby. Photo: Thomas Marent

They have sexual dimorphism (difference between males and females): the males have bulging structures on the face that increase in size as the animal grows, a long beard and mustache, the hair of the arms longer and they have a bag hanging in the throat. This bag is used as an amplifier of their calls, which can be heard two kilometers away. They use it to defend their territory and attract females. The males are also larger than the females, weighing a hundred kilos or more and they measure 1,5 m (females weigh about 40 kg and measure 1.1 m in height).

Bornean male orangutans (Pongo pygmaeus) in which the mandibular bag and cheeks are shown. Source

FEEDING AND BEHAVIOUR

Orangutans are solitary and nomadic, moving through the treetops in search of fruit. They can also feed on other parts of the plants, honey and small animals such as termites, chicks, eggs and lizards.

Although they have solitary habits, their social interaction is very complex when they meet, and adolescent females can travel together for 2-3 days. Orangutans use tools and have behaviors that they learn by imitation and vary according to the region (culture).

REPRODUCTION

Females give birth in a nest at the top of the trees. After 9 months of gestation, a single baby is born and will stay close to the mother until its maturity, about 8 years. The male does not cooperate in the breeding.

One week old orangutan hitched to her mother. Photo: ARNO BURGI/AFP/Getty Images

The reproduction rate of orangutans is very low: females reach sexual maturity at 15 and give birth every 8-9 years, so they will only have about 3-4 babys throughout its life. This means that the recovery of the species is very complicated. They can live about 50-60 years.

DISTRIBUTION

It is the only great ape living in Asia, in the rainforests of the islands of Sumatra and Borneo. Its distribution is very small due to the destruction of their habitat .

Pongo, oragutan, distribution, distribution, distribution, map, map
Distribution of the 3 species of orangutan. Source: batangtoru.org

 A NEW SPECIES: THE TAPANULI

Pongo tapanuliensis. Foto: Andrew Walmsley

In 2001 scientists defined the two orangutan species known, the Sumatran and Bornean orangutans. We will not delve much into their differences to focus on the latest discovery. Mainly, Sumatran orangutans have a flatter face than Bornean’s, (which have a concave face) and their fur is thicker, longer and clearer than Bornean’s.

Pongo tapanuliensis, the new species discovered, inhabits the Batang Toru region (North of Sumatra), an ecosystem with 85% of its forest  protected. How is it possible that a new species of such large animal has not been identified until now? Traditionally, species began to be classified according to their similarities and morphological differences, but nowadays many of these species are being redefined thanks to genetic studies.

The Tapanuli population was rediscovered in 1997, but it was not until 2013 that the study of a skull give researchers some clues about notable differences with other populations. The male skull was smaller than the other population’s skulls and also the fur was more cinnamon and curly in the Tapanuli. The morphological data were not enough, so the genome of this orangutan was sequenced and compared with the populations of Sumatran and Bornean oranguntans.

It was concluded that belonged to a new species, much older than the other two: it separated from the orangutan of Sumatra 3.38 million years ago. It is the oldest evolutionary line of Pongo (see image of the previous section) and has been isolated 10,000-20,000 years from other populations of Borneo. The research was also completed with observations of behavior (the call of the males is different, they consume other species of plants) and other facts that confirm the existence of this new species (less robust skull and jaws,  different size of the molar than fossils of the Pleistocene, males with flatter cheeks covered in fine blond hair).

THREATS

Orangutans are among the most threatened species in the world. The tendency of their populations is the decrease: since 1900, more than 91% of orangutans have disappeared. According to the IUCN , they are classified as “critically endangered” the previous step to  the extinction in the wild. It is estimated that there are 14,613 individuals of Sumatran orangutan, 11,000 Bornean orangutans and there are only 800 individuals of tapanuli orangutan left. Newly discovered, it has become the most threatened species of great apes. They could disappear in a few decades: only with the death of 8 individuals per year (1%) the extinction will be a fact.

Orangutan walking through the destroyed jungle. Photo: Hardi Baktiantoro

One of the dangers they face is the illegal trade of babys as pets. To do this, the poachers kill the mother and due to the strong bond between mothers and babys, the latter suffer traumas that mark them for life. If you want to know more about the physical and psychological consequences suffered by captive apes, do not miss reasons for NOT having captive primates. In addition, prostitution and sexual abuse of female orangutans is a common practice.

However, the main threat of the orangutan is the destruction of its habitat. The destruction of the forest for logging, mining and agriculture was reduced by 60% between 1985 and 2007. The Tapanuli only occupy an area of ​​1,000 km2.

Deforestation of Borneo from 1950 to 2020. Source: UNEP / GRID-Arendal Maps and Graphics Library

Unfortunately , orangutans have become the visible face of the loss of biodiversity due to the extensive cultivation of palm Elaeis guineensis. Its oil is used worldwide in all types of products, especially in bakery, snacks and prepared food, cocoa creams and even cosmetics and agrofuels. Without forgetting the implications for the health of this low quality oil and the contamination caused by the destruction of waste during the production, the uncontrolled clearing of trees and fires of large areas of forest to grow the palm is killing the orangutans (thousands die every year), among other species such as the Sumatran tiger. Orangutans are also killed directly, either by entering the crops and occasionally to be marketed as food (bushmeat).

Orangutan with burns victim of deforestation for the palm oil industry. Photo: unknown

To learn more about the ecological crisis of Southeast Asia, do not miss this interview that we did to Joana Aragay, a biologist who lived firsthand the fires of 2015 in Borneo.

WHAT CAN YOU DO?

Aye-aye: the strangest primate

With a peculiar appearance and way to find food, the aye-aye is perhaps the rarest primate that exists. It is also rare for its distribution and specimens: it is endemic to Madagascar and it is in risk of extinction. Find out in this post why the aye-aye is special.

THE AYE-AYE IS A PROSIMIAN

The aye-aye is the only species of the Daubentoniidae Family. It was believed to have been extinct until its rediscovery in 1957. Although it is hard to believe, the aye-aye is a primate like us. Some authors consider it a type of lemur.

Aiye-aye (Daubentonia madagascariensis). Photo: Frans Lanting

Its strange name is believed to come from the Malgasy expression “heh heh“, which means “I do not know”, to avoid naming it as it is considered as an animal that represents evil according to some traditions.  “Hai hai” or “hay hay” is also a common name on the island of Madagascar that could have given the animal its name.

Because it is a prosimian, the oldest group of primates, it has particular carachteristics. The prosimians are characterized by:

  • Claws instead of nails (they have at least one nail)
  • Long snout with moist nose. They are the primates with the greater sense of the smell
  • Bigger lateral orientation of the eyes than other primates. These are large and have good night vision
  • Mobile hearing pavilions
  • They have the lower cerebral proportion of primates

If you want to know more about classification and characteristics of primates, you can visit the post Who are the hominids?

APPEREANCE AND BEHAVIOR

The aye-aye has a black-brown coarsed fur covered by white hairs as  a protection. It has a leafy tail as long as its own body. They measure up to 40 cm and weigh up 2.5 to 3 kg, making them the largest nocturnal primates.

Its eyes and auditory pavilions are large and its fingers are slender, with claws in all of them, which allows them to hang from the branches. It is therefore exclusively arboreal. To climb it performs small vertical jumps like squirrels do, and it avoids treading the ground of the rainforest in which it lives, in the North and East of Madagascar.

Front view of aye-aye and its claws. Photo: Dani Jeske

They have nocturnal and solitary habits and they spend the day resting between the junction of the branches or in a kind of nest made of branches and leaves. These nests have the appearance of spheres with an entrance hole, they are located between the branches of large trees and are occupied by successive aye-ayes, they are never shared.

DIET

The aye-aye feed mainly on seeds of Canarium spp, a tree, which determines its distribution. It also eats fruits, including coconut pulp, other seeds and fungi.

But they are also attracted to insect larvae, and their way of finding them is almost exclusive: it gives small strokes on the bark of the trees with their thin third finger (up to 8 times/second), and then it listens the presence of larvae inside the hollow chambers, in a way similar to echolocation  (it is the only primate that uses echolocation).

 Detail of lmano del Aye-aye, with the thin third finger and the long fourth finger. Photo by Mark Carwardine
Aye-aye hand detail, with the slender third finger and the long fourth finger Photo: Mark Carwardine

Like the woodpecker, which also feeds on larvae from within the trees, the aye-aye uses the frontal teeth to chew the bark. Its frontal teeth are always growing as rodent teeth do, and with the third or fourth finger, which is the longest and with a double joint, extracts the larvae. Here’s how aye-aye’s do it in this short video:

This method of finding food is known as percussive foraging. The only other animal known to use this strategy is the stripped possum  (Dactylopsila trivirgata), an Australian marsupial.

Stripped possum. Photo: Peter Bray
Stripped possum. Photo: Peter Bray

REPRODUCTION

Although they are solitary, there is evidence that aye-ayes also feed on tandem and exhibit different relationships between animals of the same sex (Sterling and Richard 1995). The territories of different males can overlap each other, as well as the terriotories of several females. These territories are marked with scents.

Females are fertile at 3-4 years old and can give birth every 2-3 years (Petter and Peyrieras 1970). There is no season of mating and after gestation a single young is born.

Aye-aye de un día de vida siendo pesado dentro de un programa de cría en cautividad. Foto: David Haring
One year old aye-aye being weighed within a captive breeding program. Photo: David Haring

THREATS AND CONSERVATION

Aye-aye is considered by the IUCN Red List as endangered. The trend of the population is decreasing, and in the last 30 years more than half of it has disappeared. The main cause is the decline and degradation of their habitat, as well as the exploitation of the forest through unsustainable ways of hunting. These causes have not ceased and they are not easily reversible, so it is estimated that in 10-20 years more than 50% of the population will disappear. If you want to know more about the threats to Madagascar, visit Madagascar, a paradise in danger.

Distribución del Aye-aye en Madagascar, África. Fuente
Distribution of aye-aye in Madagascar, África. Source

In addition to habitat destruction and its hunting as food, it is also killed in some areas as a bad omen, an evil incarnation or a pest for crops (eg coconut).

Aye-aye cazado y colgado para que los viajeros se lleven su espíritu maligno, según algunas tradiciones malgasias. Foto: Thomas Althaus
Aye-aye hunted and hung for travelers to take away their evil spirit, according to some Malagasy traditions. Photo: Thomas Althaus

Some populations are in protected areas within National Parks and reserves. There are also captivity breeding programs to study the aye-aye and its subsequent reintroduction of the species in their habitat, which began in the 60s, since their populations are fragmented and with low density of individuals. Even so, the second generation has not succeeded in reproducing in captivity.

It is difficult to establish the number of individuals, which have evasive and nocturnal habits. Their presence is assumed by the marks that they leave in the trees, although a single individual can leave several marks. It is suspected that the aye-aye has the least genetic diversity of all lemurs. More research and census of aye-aye are needed to understand more about its population dynamics and biology.

REFERENCES

MIREIA QUEROL ALL YOU NEED IS BIOLOGY

It’s a matter of horns

Some beetles, lizards... have horn-like structures, but mammals have the most diverse horns without doubt. Are all horns the same? What are they used for? Do they have economic value? Find out more in the following post.

WHAT ARE HORNS?

Bulls, deer, rhinos… all of them have structures on their heads that we call horns, but they are not all the same. Strictly horns are two bony structures that emerge from the frontal bones of the skull, they are permanent (never fall off) and unbranched. In some species they grow throughout life.

El watusi, el bóvido con los cuernos más grandes del mundo. Foto: Marina Calvo
Watusi (Bos taurus watusii), the bovid with the biggest horns in the world. Photo: Marina Calvo

They are made up of a bony nucleus and an outer coating of keratin (the same protein from our hair and nails).

Horns have different shapes and sizes depending on the species: straight, curved or spiral; flipped, bent or flat; short or wide. All of them have sharp ends.

Diversidad de cuernos de la familia Bovidae. Fuente
Horns’ diversity of Bovidae. Source

All bovids (bulls, goats, sheep, antelopes…) have horns, including the females in many species. However, in general, females have thinner horns while in males they are wider and can withstand more force.

HORN GROWTH

When the horns begin to grow, they do not do it directly from the bone, but from the connective tissue. When growth is complete the horn nucleus ossifies and fuses with the frontal bones of the skull.

Cráneo de cabra en el que se observa el interior óseo del cuerno y la cubierta queratinosa. Fuente
Goat skull showing the bony interior of the horn and the keratinous covering. Source

AN EXCEPTION

The pronghorn has different horns than the bovids: they are branched and the keratinized covers change annually, whereas in bovids are permanent.

Berrendo (Antilocapra americana). Fuente
Pronghorn (Antilocapra americana). Source

WHAT ARE ANTLERS?

Antlers are two bony structures that come out of the frontal bones, but they are seasonal (they change every year) and branched .

Antlers only exist in males of the Cervidae family, except for the caribou or reindeer (Rangifer tarandus), in which both males and most of females have antlers.

GROWTH OF THE ANTLERS

Unlike horns, antlers do grow out of bony structures (pedicle) found on the side of the frontal bones.

Growth begins in spring (April or May in the Northern Hemisphere), due to hormonal changes and the gradual increase in light hours. The growth of the antlers has several phases:

  • Initial phase: antlers are covered with skin and velvet, so they also have blood vessels and nerves.
  • Intermediate phase: the exterior of spongy bone is replaced by compact bone. The interior is filled with spongy laminar bone.
  • Final phase: the velvet dies and it is removed. To help this removing the animals rub against the trunks and vegetation, leaving the antlers polished and brown.

    A, B, C: 1, 15 y 30 días de crecimiento. D, E: 3 y 5 meses después.F: pérdida del terciopelo. Fotos: A-E, Steve Demarais, F, Dave Hewitt.
    A, B, C: 1, 15 y 30 days of growht. D, E: 3 and 5 months later. F: loss of the velvet. Photos: A-E, Steve Demarais, F, Dave Hewitt

After the reproductive period the hormonal levels fall and the photoperiod decrease, which causes the pedicle to lose calcium, it weakens the union between itself and the horn and the horn ends up falling. The cycle will be repeated the following spring, and will appear one more branch, so the most an antler is branched, the older is the individual.

Alce pediendo su terciopleo. Fuente
Reindeer losing its velvet. Source

USES OF HORNS AND ANTLERS

As we know, mainly antlers and horns are used by males during the breeding season to compete for females, in fights and exhibitions. Usually the animals collide their horns/antlers together to demonstrate their body strength. Horns, often sharp, are also used as a defense against predator attacks.

Check out this spectacular dispute between two Canadian mouflons:

There are species with small antlers but highly developed tusks, despite being herbivores. This is because they also use them during fights. In contrast, species with larger antlers do not have these developed tusks.

Siberian musk deer (Moschus moschiferus) - does not belong to the family Cervidae-, Muntjac (Muntiacus sp.) And roe deer (Capreolus capreolus)
Siberian musk deer (Moschus moschiferus) -it does not belong to the family Cervidae-, Muntjac (Muntiacus sp.) and roe deer (Capreolus capreolus). Source

For humans, horns and antlers shouldn’t have significance. Unfortunately, its carriers are objective of hunters, for the mere achievement of their “trophy.” In Spain there are more than one million people with a hunting license. According to Fecaza, the hunting business generates 3.6 billion euros a year in Spain.

Trofeos de caza robados incautados por la Guardia Civil. Su valor pudo ascender a 300.000 euros. Fuente
Stolen hunting trophies seized by the Guardi Civil. Its value could amount to 300,000 euros. Source

Spain is also the second importing country of hunting trophies. Thousands of euros are paid (from 2,000 to 80,000) to make hunting safaris in Africa, for example, where the most valuable animal is the one with the largest horns. This results in the elimination of the best breeding males and in the decrease of specimens in general.

AND THE RHINOCEROS HORN?

Ironically, since their horns have led and are leading to extinction many species, rhinos do not actually have real horns, as they do not have a bony nucleus or a cover. They are an accumulation of corneous fibers, resembling a thick hair, although they are not true hairs. In addition, the horn is placed above the nasal bones, not  in frontal position as in the case of antlers and true horns. Only in species with two horns, the second one rests on the frontal bones.

In females, the horn would help to protect the young, whereas in males to face their rivals.

Sección de un cuerno de rinoceronte cisto bajo lus ultravioleta. Se observa el cartílago nasal, el hueso, la dermis y cómo el cuerno se asienta encima de la dermis. Fuente
Fraction of a rhinoceros horn under ultraviolet light. The nasal cartilage, the bone, the dermis and how the horn settle in above the dermis can be seen. Source

As we have discussed, due to the alleged magical powers of rhinoceros horns in the traditional medicine, we are extinguishing rhinoceroses just like with are doing with the pangolin… for a handful of keratin. On the black market, a kilo of rhinoceros horn can cost from $ 60,000 to $ 100,000, more than gold.

Rinoceronte con el cuerno amputado.
Rhinoceros with its horn amputated. Photo: A. Steirn

HAVE YOU NOTICED GIRAFFE’S HORNS?

As you may assume at this point, no, giraffes do not have true horns, but they also have two structures in the head, males, females and newborns. They are called ossicones. They are permanent, not branched and they are always covered with hair and skin. In fact, they already appear in the fetus as cartilaginous structures and do not merge into the skull until the age of 4, between the frontal and parietal bones.

Female giraffe (Giraffa camelopardalis). Source
Female giraffe (Giraffa camelopardalis). Source

We can tell age and sex of a giraffe by its ossicones: if they are thin and ended up in a tuft of hair they are young ones or females, while males do not usually have hair on its top. Males also have a protrusion in front of the ossicones more sharp than females. At an older age, this protuberance is bigger, since calcium is deposited over time.

Giraffe ossicones are used by males during their confrontations. Surely they played a more important role in its ancestors like the Sivatherium, the largest giraffid that has ever existed. It is possible that they also have some function in thermoregulation.

REFERENCES

MIREIA QUEROL ALL YOU NEED IS BIOLOGY