Arxiu de la categoria: Marine mammals: Behavior and life history

How do cetaceans communicate?

We cannot imagine our lives without communication, but we are not the only animal species that use communication as a way to exchange information. In this post, we are explaining how cetacean’s communication is.

HOW DO CETACEANS COMMUNICATE?

Given that there are highly social species among cetaceans, it is essential to understand the role that communication plays in regulating social interactions in these species. When we think of communication, we usually tend to associate it with acoustic communication, and, in fact, this is the major way for cetaceans; but other types exists, such as chemical, visual or tactile communication.

ACOUSTIC COMMUNICATION: THE MOST DEVELOPED

Acoustic communication is the most important way of communication in cetaceans and the reason is that sound transmission in the water is very fast. It includes both vocal and non-vocal signaling. In some species, it can be very complex, since some of them have dialects.

Because of the fact cetaceans rely on sound, some activities such as seismic surveys may interfere in their behaviour and threaten their survival.

NON-VOCAL COMMUNICATION

Non-vocal communication consists of producing sounds without using the vocal apparatus, like using flukes or flippers to strike the water surface, jaw claps, teeth gnashing or bubble emissions. By slapping their tails, cetaceans convey a threat or distress.

Breaching is the typical behaviour of most cetaceans in which they leap vigorously into the air. The originated sound may travel several kilometres and it is thought to be a spacing mechanism, to keep acoustic contact or to inform about sexual stimulation, location of food or a response to injury or irritation. It can also be a manner to remove parasites and dead skin. More studies about the purpose of breaching are needed.

VOCAL COMMUNICATION IS VERY COMPLEX IN CETACEANS

Considering vocal communication, odontocetes and mysticetes  are very different. For this reason, we are explaining it separately.

MYSTICETES

Sounds of baleen whales have a social function, such as contact when in long distances, assembly calls, sexual advertisement, greeting, spacing, threat and individual identification. It is probable that they use sound as a way to synchronise biological or behavioural activities, such as feeding or breeding. You can read more about communication in baleen whales here.

Scientists agree there are three (plus one) types of sound in mysticetes:

  • Low-frequency moans (1-30 seconds, 20-200Hz). These sounds can be pure tones, such as in the case of fin whales (Balaenoptera physalus), or complex sounds with harmonic structure. These sounds are used in communication at long distances. For example, 20Hz moans of humpack whales (Megaptera novaeangliae) can pass through most obstacles and travel hundreds of kilometres to reach conspecifics for signaling. It has been suggested that, without obstacles, these kind of sounds can travel from pole to pole. Amazing, isn’t it? You can hear the call of the fin whale here.
fin whale, rorqual comun, balaenoptera physalus, circe, whale communication, cetacean communication, comunicacion ballenas, comunicacion cetaceos
Fin whale (Balaenoptera physalus) (Picture: Circe).
  • Short thumps or knocks (< 1 second, < 200Hz). These sounds are known to be produced by right whales (Eubalaena sp), bowhead whale (Balaena mysticetus), gray whales (Eschrichtius robustus), fin whales and minke whales (Balaenoptera acutorostrata).  These sounds are related to social context and activity.  You can here the call of the gray whale here.
  • Chirps and whistles (>1kHz, <0.1 seconds). These sounds are produced by most baleen whales. 
  • Humpback whale songs. You can here some songs of humpback whales here:

ODONTOCETES

According to scientist, odontocete sounds can be divided into two categories:

  • Pulsed sounds. All toothed cetaceans produces this type of sounds and can be used for echolocation (the production of high-frequency sound waves and reception of echoes to locate objects and investigate the surrounding environment) or communication. echolocation, dolphin, ecolocalizacion, delfines, comunicacion odontocetos, odontocete communicationEcholocation in dolphins.

They can be subdivided into two types:

  • Pulse or click trains (clicks). Click trains consist of sequences of acoustic pulses (50μsec, 5-150kHz) repeated over time. They are related to echolocation. Species can have a broad spectral composition, such as in the bottlenose dolphins (Tursiops truncatus), or have a narrow-band composition, as in narwhals (Monodon monoceros). In this type of pulsed sound, animals produce from 1-2 to serveral hundreds of click per second. You can hear the clicks of the bottlenose dolphin here.
  • Burst-pulsed sounds (20-100kHz). These high repetition rate pulse trains; called barks, squawks, squeaks, blasts, buzzes and moans; consists of producing a pulse every less than 5μsecond, which is heard by humans as a continuous sound. They have  communicative and social functions. You can hear burst-pulsed sounds in an aggressive encounter among dolphins in this video:

  • Narrow-band tonal sounds (whistles) (5-85kHz). Whistles are thought to be produced only for communication purposes and not all odontocetes produce them. Because they are low frequency sounds, these sounds can travel longer distances than pulsed sounds. Some species, such as bottlenose dolphins can produce whistles and clicks at the same time, what permits to maintain communication and coordination during food search by echolocation. Even in some species, such as the bottlenose dolphins, exists signature whistles; that is a so distinctive whistle that serve to identify the animal, as if it was its name. Do you want to know more about signature whistles? Watch the video:

CHEMICAL COMMUNICATION IN CETACEANS

Chemical communication includes the smell and taste. Despite it is important in terrestrial mammals, in marine mammals it is limited.

The olfactory system in cetaceans is almost nonexistent, since there is no olfactory nerves, bulbs and tracts in adult odontocetes (cetaceans with teeth) and they are greatly reduced in adult mysticetes (baleen whales). In addition, all cetaceans close their blowholes under the water.

On the other hand, taste is more important. For example, bottlenose dolphins (Tursiops truncatus) have the ability to discriminate sour, sweet, bitter and salty solutions. However, they are least sensitive to different salt concentrations, being adaptive to the  marine environment.

delfin mular tursiops truncatus comunicacion cetaceos
Bottlenose dolohins (Tursiops truncatus) can discriminate sour, sweet, bitter and salty solutions (Picture: NASA, Creative Commons).

Other species, such as belugas (Delphinapterus leucas), release pheromones to alarm their mates and, with blood in the water, they quickly escape or become unusually excited.

VISUAL COMMUNICATION

Vision under water is limited by light levels, the organic matter and depth. Visual displays can be of different types, such as sexual dimorphic features, body postures and colouration patterns, which are simple; or more complex like sequences of behaviours, which indicate a context, species, age, sex or reproductive condition.

For cetaceans, visual signals are an alternative to acoustic communication when the animals are close. In the case of odontocetes, visual displays are behaviours, colouration and morphological traits.

For example, male narwhals have long spiral tusks and in males of several beaked whales there are lower teeth that protrude outside the mouth. In that cases, but they are not the only ones, these are sexually dimorphic features that may play an important role in regulating social signaling and mating.

narwhal, narval, monodon monoceros, comunicacion cetaceos
Male narwhals (Monodon monoceros) have a spiral tusk that may regulate social signaling and mating (Picture: NOAA).

Clear-water dolphin species show colour patterns in the body, such as spots, saddle patches, capes or longitudinal striping, such as the striped dolphin (Stenella coeruleoalba).

Stenella coeruleoalba delfin listado cetáceos mediterraneo
Striped dolphin (Stenella coeruleoalba) (Picture: Scott Hill National Marine Mammal Laboratory, Creative Commons).

Finally, gestures are also important in cetaceans, such as open-jaw threat displays, aerial leaps, flared pectoral fins, tail lobs and S-shaped postures. Posture and behaviours may also inform about predators, prey or to synchronise actions among individuals in order to coordinate the group or for social interaction.

In this video, you can see a dolphin displaying the open-jaw threat behaviour.

In this one, a humpback whale is showing the tail lob display.

COMMUNICATION THROUGH TOUCH

Cetaceans may use their nose, flippers, pectoral fins, dorsal fin, flukes, abdomen and the entire body as a means of communication by touching other animals.  Tactile signals are usually used together with other types. This type of communication has been noted in all cetaceans. Not only do body contact serve as a communication display, but it also may serve to remove dead skin.

For example, gray whales (Eschrichtius robustus) of San Ignacio Lagoon (Mexico) rub under small boats and tolerate petting of tourist.  You can watch it here:

Atlantic spotted dolphins (Stenella frontalis), bottlenose dolphins, humpback whales and North Atlantic right whales (Eubalaena glacialis), among others, gently rub their bodies with congeneres and it is common between mothers and calves.

REFERENCES

  • Berta, A; Sumich, JL & Kovacs, KM (2006). Marine mammals. Evolutionary biology. UK: Academic Press.
  • Dudzinkski, KM; Thomas, JA & Gregg, JD (2009). Communication in Marine Mammals. In Perrin, WF; Würsig, B & Thewissen, JGM (Ed.). Encyclopedia of Marine Mammals (260-269). Canada: Academic Press.
  • Cover picture: Gregory “Slobirdr” Smith, Creative Commons.

Have you ever seen some of these types of communication in cetaceans? Share it with us on the comments!

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Dolphins and humans: 5 things in common

Dolphins awaken interest of most people, if not everybody. Some of them are attracted by these creatures for their intelligence. Others because they believe they have a special connection with them. Whatever the reason, the fact is that there are some behaviours and characteristics of these wonderful animals that are shared with humans. Do you dare to find out?

1. DOLPHINS HOLD CONVERSATIONS

According to a study published in August 2016 in the journal Mathematics and Physics, scientists have discovered what appears to be a type of spoken language of dolphins.

Specifically, they have found that two dolphins took turns at the time of producing sound pulse packs and they  do not interrupted the other while the partner was communicating. Some people should learn from the dolphins, don’t you think? Scientists have compared it to a conversation between two people.

Tursiops truncatus delfin mular
Two dolphins have been described holding a conversation, in the same way as people do it (Picture: Julien Bidet, Creative Commons).

It is the first time that this phenomenon has been detected. Now, thanks to microphones that distinguish the different “voices” of animals, it has been possible.

But they have not only reached this conclusion. They also believe that each sound pulse corresponds to a word and pulse packs are actually phrases, in the same way that humans do. This means that the two individuals were sharing some kind of message.

All this demonstrates the high level of intelligence and conscience of these animals, besides the level of development of their spoken language, comparable to humans.

Do you want to know about some cetaceans with dialects?

2. DOLPHINS ALSO HAVE A NAME

To be more correct, dolphins have identification whistles that allow the identification of individuals, called signature whistles. Calves develop over time its own whistle, which seems to be part of their imprinting.

Imprinting is a pattern of rapid learning and normally stable that appears early in life of a member of a social species, and implies the recognition of their own species. This may involve attraction to the first seen moving object, even another species.

It is not after two months of life that they develop their signature whistle. At the time of “choosing its name”, they seek a whistle different from the other members’ group to avoid confusion.

Another study from 2013 concluded that dolphins respond when they hear that another individual “says its name.” It also showed that in case animals are exposed to signature whistles that are not of any member of the group, they do not respond.

You can find more information in this video from National Geographic:

3. MOTHERS TALK TO THEIR BABIES WHEN THEY ARE IN THE UTERUS

What pregnant woman has not sung or spoken to her babies as they were being developed in the womb? According to experts, this helps the baby to recognise her voice. We now know that we are not the only species who do it.

A research suggests that mothers talk to their babies. Specifically, they sing their own name. This is believed to help the baby to recognise her mother’s voice.

delfín útero feto
Dolphin mothers sing to her babies while they are in the womb (Picture: National Geograhic).

The songs are intensified two weeks before birth and last until two weeks later. The funny thing is that the rest of the group significantly reduce production of its signature whistle during the first two weeks of life of breeding.

4. SEX: BEYOND THE PROCREATION

How many animal species do you know that have sex for pleasure? It is known that several species of dolphins, like humans, bonobos and other species, have sex beyond procreation.

This is known to be true because females have been watched having sex beyond their period of ovulation. It is also known that killer whales, the larger dolphin species, have homosexual behaviours.

In addition to feeling pleasure, these “encounters” can serve to strengthen the links between the different members of a group.

I leave this other video of National Geographic in which promiscuity dolphins is explained:

5. DOLPHINS USE PROTECTIONS TO AVOID INJURY

A study reported that bottlenose dolphins (Tursiops truncatus) use sea sponges, supposedly to avoid getting hurt with rocks when  they are looking for something to eat or to avoid the pincers of crabs.

delfin sponging tursiops truncatus delfin mular
A bottlenose dolphin (Tursiops truncatus) with a sea sponge in the snout (Picture: Eric M. Patterson)

This behaviour has been named sponging. This practice cannot be extended to all individuals of the species, as it has only been described in a region of Australia.

It is believed that this behaviour has passed between generations, from mother to female offspring (very little in males), but there was only one inventor, that had the occurrence between 120 and 180 years ago.

In addition, scientists have found that females who use sponges, compared to those in the area which do not use them, are more lonely, spend more time in the depths and spend more time feeding, without compromising the future of their offspring.

5+1. DOLPHINS LOVE TECHNOLOGY

OK… That is not true! But look this video of a captive dolphin, which steals woman’s iPad.

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Which of these facts have you found more surprising? Do you know other dolphin behaviours that are similar to humans? Leave your answers in the comments.

REFERENCES

Difusió-anglès

The elderly organisms of the oceans

Have you ever wondered which are the longest-lived organisms of the seas and oceans of the Earth? The sea turtles are well known to have long lives. But, ¿which is the oldest organism of the ocean (and the planet)?

BOWHEAD WHALES

The bowhead whales (Balaena mysticetus), also called Arctic right whales, live most of the year associated with sea ice in the Arctic ocean. These marine mammals are among the largest animals on Earth, weighing up to 75-100 tons and with a length of 14-17 m on males and 16-18 m on females.

Bowhead whale (Balaena mysticetus) (Picture: WWF).
Bowhead whale (Balaena mysticetus) (Picture: WWF).

More than 20 years ago, in 1993, it was discovered by chance that bowhead whales have a longer life than previously thought. Their lifespan was considered to be about 50 years, but the unexpected discovery let to know that they live more than 100 years. In fact, some individuals are known to have lived for about 200 years.

Which was that fortuitous discovery? An Alaskan Eskimo hunted an individual with the tip of a harpoon inside its blubber. This harpoon was created with a technique not used for 100 years.

They are among the mammals that get much older, even among other whales. And the explanation to this fact lies on the extreme cold of their habitat: they have to invest so much energy in maintaining the body temperature that their first pregnancy is usually at 26 years and, therefore, they have a long life expectancy.

SEA TURTLES

In the famous Disney movie Finding Nemo, Marlin, Nemo’s father, meets Crush, a 150-year-old sea turtle. However, do sea turtles live so much?

Do you want to discover the amazing life of the sea turtles? Do you want to know the reason why sea turtles are threatened?

Sea turtles have long lives, but their age is unknown (Picture: Key West Aquarium).
Sea turtles have long lives, but their age is unknown (Picture: Key West Aquarium).

It is well-known that sea turtles have a long life, but their ages are barely known. It has been confirmed that growth lines in some turtle bones are laid down annually, but due to growing at different rates depending on the age, this cannot be used to estimate their age.

However, scientist believe that these awesome reptiles may live long like whales. Those turtles that outlive the first stages of life can expect to live at least 50 years. In addition, biological aging is nearly suspended for these animals.

Despite unknowing the age of the oldest wild sea turtle, it is said to be a 400-year-old captive sea turtle in China.

THE OLDEST KNOWN ANIMALS

Black corals are the oldest known animals on Earth. Notwithstanding, they are not the oldest organisms on the planet.

Leiopathes sp. is a genus of black corals that can live several millenniums (Picture: CBS News).
Leiopathes sp. is a genus of black corals that can live several millenniums (Picture: CBS News).

These coal-dark-skeleton corals grow a great deal less than a millimetre per year, such as the Mediterranean red coral. Despite its name, they usually show yellow, red, brown and green colours. Although they are considered deep-sea corals, they are found worldwide and at all depths.

Research in 2009 demonstrated that a Hawaiian black coral individual included in the Leiopathes glaberrima species had been living and growing since the building of Egyptian pyramids; 4,600 years ago.

Like sea turtles, in case an individual survives the first century of age, there is every likelihood of  living for a millennium or more.

THE IMMORTAL JELLYFISH

It is a fact of life that all living beings die; except for Turritopsis nutricula, the immortal jellyfish. This small (4.5 mm) bell-shaped jellyfish is immortal owing to the fact that possess the capability to age in reverse.

The immortal jellyfish, Turritopsis nutricula (Picture: Bored Panda).
The immortal jellyfish, Turritopsis nutricula (Picture: Bored Panda).

This species starts its life being a mass of polyps growing in the seafloor, which in some point produce jellyfishes that develop gonads to create the following generation of polyps, and then die. This has nothing special in comparison with other jellyfishes. Learn more about these beautiful animals here.

This cnidarian species, under the presence of a stressor or injury, transforms all its cells into larval forms. It is that changes from an adult to a larva. Then, every single larva can transform into a new adult. That process is named transdifferentiation. Little do scientists know about this process in the wild.

Transdifferentiation in Turritopsis nutricula (Picture: Bored Panda).
Transdifferentiation in Turritopsis nutricula (Picture: Bored Panda).

THE OLDEST ORGANISM ON EARTH

The oldest organism on Earth is neither an animal, algae nor a microorganism. The most elderly organism in the planet is a plant. In concrete, a marine plant known as Posidonia oceanica, commonly known as Neptune Grass or Mediterranean tapeweed. Do you want to know the reason why the Posidonia ecosystems are considered the marine jungles?

pradera posidonia oceanica
Posidonia oceanica meadow (Picture: SINC).

Spanish researchers found out that in Formentera (Balearic Islands) there is a 100,000-year-old Posidonia clone. This means this is the longest-living organism on the biosphere.

The key to understand its age is the clonal growth: it is based on the constant division of cells placed in the meristems and on the extremely slow growth of its stalk (rhizomes).

REFERENCES

  • Arnaud-Haond S, Duarte CM, Diaz-Almela E, Marba` N, Sintes T, et al. (2012) Implications of Extreme Life Span in Clonal Organisms: Millenary Clones in Meadows of the Threatened Seagrass Posidonia oceanica. PLoS ONE 7(2): e30454. doi:10.1371/journal.pone.0030454
  • NOAA: Black corals of Hawaii
  • Palumbi, S.R & Palumbi, A.R (2014). The extreme life of the sea. Princepton University Press
  • Reference: The oldest sea turtle
  • Rugh, D.J. & Shelden, K.E.W. (2009). Bowhead whale. Balaena mysticetus. In Perrin, W.F; Würsig, B & Thewissen, J.G.M. Encyclopedia of Marine Mammals. Academic Press (2 ed).
  • Schiffman, J & Breen, M (2008). Comparative oncology: what dogs and other species can teach us about humans with cancer. The Royal Society Publishing. DOI: 10.1098/rstb.2014.0231
  • WWF: How long do sea turtles live? And other sea turtle facts
  • Cover picture: Takashi Murai (Bored Panda)

Difusió-anglès

Breeding in seals and social organitzation

Pinniped species, commonly known as seals, breed on land or ice. Depending on the place they breed on, they present a social organization or another. In this post, we will review both the breeding systems in seals and their social organization. Do you know that in the Mediterranean Sea live seals? 

MATING AND BREEDING IN PINNIPEDS

Pinnipeds have different mating systems: while most of the species are polygynous, it is that males mate with several females; others are monogamous and males mate with just one female during a breeding season. In the first case, males are much larger than females, while in the monogamous system there are almost no differences between sexes.

Like in the rest of species, females are more valuable than males because they produce the ovule, carry and nourish the young, produce milk after birth and provide all parental care. On the other side, it is much better for males to copulate with as many females as possible to increase their reproductive success. Therefore, maternal nurturing plays a key role in organising their societies. 

Pinnipeds use different habitats for their breeding:

  1. Land
  2. Ice: both pack ice (floating ice) and fast ice (ice attached to land).

In the following sections, we will explain the mating and breeding systems in each type of seal, in addition to their social organization.

LAND-BREEDING SEALS

20 of the 33 pinniped species breed on land, specially on islands because are more favourable than mainland beaches and sandbars (where they can also breed on).

South-American-sea-lion--bull
South American sea lions (Otaria bryonia) breed on land (Picture: Steven Hazlowski, Arkive).

However, there are neither many favorable islands to seals nor many suitable breeding sites in these islands and, thus, females and pups tend to congregate in colonies, where males either compete for breeding territories (in otariids, it is sea lions and fur seals) or establish dominance hierarchies (in elephant seals). 

Cape-fur-seal-colony
South African and Australian fur seals (Arctocephalus pusillus) live in large colonies (Picture: Pete Oxford, Arkive)

These aggregations let males copulate with a great number of females (after an intense competition among males).

Among the species that breed in large colonies, there are a marked variability in the social organization. Some species form annual breeding aggregations at traditional locations called rookeries. Rookeries are formed by all otariids, elephant seals and gray seals. During this period, females and pups live in zones controlled by alpha males, while juvenile and subdominant males live in bachelor groups.

Even during the nonbreeding season, they  usually live in association with other animals because it gives some advantages:

  • Thermoregulatory effects of huddling together during cold weather.
  • Protection from predators.

ICE-BREEDING SEALS

Different from the land-breeding seals, ice-breeding species on pack ice are not obliged to form aggregations due to the vast available ice and, therefore, males cannot mate with so many females, just one or a few females.

Ross-seal
Ross seal (Ommatophoca rossii) chiefly live on dense consolidated pack ice. They are usually solitary or live in small groups (Picture: NOAA, Creative Commons).

So, it is common in seals that breed on pack ice to be monogamous or slightly polygynous. 

On the other side, seals can breed on fast ice (ice which is attached to land), usually in cracks and open holes. Therefore, they live in small to moderate-sized groups where a male can mate with only some females close to these particular points.

Pusa_hispida_pup
Fast-ice breeding seals, such as ringed seals (Pusa hispida) live in small to moderate-sized groups (Picture: Shawn Dahle, Creative Commons).

In general, ice-breeding seals of both sexes have a similar size, with the exception of the hooded seal (Cystophora cristata) and the walrus (Odobenus rosmarus), in which males are bigger than females; and of the Antarctic Weddell seal (Leptonychotes weddellii), in which females are bigger than males. The reason is that males maintain aquatic territories beneath the ice near holes and cracks and being smaller makes easier to protect territories and mate with females.

Phoque_de_Weddell_-_Weddell_Seal
In Weddell seals (Leptonychotes weddellii), females are bigger than males (Picture: Samuel Blanc, Creative Commons).

CONCLUSION

In conclusion, when the available space is limited, female seals congregate in large colonies, where males can mate with several females; while when the space is dispersed, females are isolated and males can mate with just one female and colonies are not formed.

REFERENCES

  • Acevedo-Gutiérrez, A (2009). Group Behaviour. In Perrin, W; Würsig, B & Thewissen, JGM (ed.). Encyclopedia of Marine Mammals. Academic Press (2 ed).
  • Antonelis, GA (2009). Rookeries. In Perrin, W; Würsig, B & Thewissen, JGM (ed.). Encyclopedia of Marine Mammals. Academic Press (2 ed).
  • Berta, A (2009). Pinnipedia, Overview. In Perrin, W; Würsig, B & Thewissen, JGM (ed.). Encyclopedia of Marine Mammals. Academic Press (2 ed).
  • Mesnick, S. & Ralls, K (2009). Mating Systems. In Perrin, W; Würsig, B & Thewissen, JGM (ed.). Encyclopedia of Marine Mammals. Academic Press (2 ed).
  • Riedman, M (1990). The Pinnipeds. Seals, sea lions and walruses. University of California Press.
  • Shirihai, H. & Jarrett, B (2006). Whales, Dolphins and Seals. A field guide to the marine mammals of the world. Bloomsbury.
  • Main Picture: Ecotrust

Difusió-anglès

Cetaceans with dialects: the killer whale and the sperm whale

Last week, the press was full of news about a recent article that highlight that sperm whales in the Eastern Pacific have distinct dialects. For this reason, the post of this week will explain what a dialect is (in cetaceans), which cetaceans have dialects in addition to sperm whales and which is the explanation to this. 

INTRODUCTION

The first question to be answered is “What is a dialect?”. This question is not simple because sometimes this concept is confused with another one: geographic variation. While dialects are song differences between neighbouring populations of potentially interbreeding individuals, geographic variations refer to differences in song over long distances and between populations which normally do not come together. In the case of dialects, the explanation of their presence is social learning, while in geographic variations the reason can be found in their genes. The function of dialects is to be an acoustical signature that help maintain cohesion and integrity of groups and as an inbreeding avoidance mechanism.

CETACEANS WITH DIALECTS

To date, dialects have been described in two cetacean species: killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus). These two species have several features in common:

  • They live in matrilineal groups, that are highly stable groups of individuals linked by maternal descent that protect themselves against predators and other dangers.
  • They live in multilevel societies, that consist of hierarchically nested social levels. From the upper to the lowest level, there are three levels: vocal clans, social units and individuals. This kind of societies are also present in human and other primates and in African elephants.

KILLER WHALE DIALECTS

Dialects have been found in resident killer whales from the northeastern Pacific, Norway and Kamchatka. In this species, these dialects consists on repertories of several call types that are different among pods. Each pod have distinctive features in the call repertories and, therefore, each pod has a particular dialect. Pods that share part of the repertories constitute acoustic clans. So, each clan is acoustically different. Pods from different clans can overlap and interact and new pods can be formed by fission of other pods, which turn out in divergence of dialects.

Killer whales are one of the cetacean species with dialects (Picture: Oceanwide Science Institute).
Killer whales (Orcinus orca) are one of the cetacean species with dialects (Picture: Oceanwide Science Institute).

SPERM WHALE DIALECTS 

Sperm whales have repertories that varied in the proportional usage of different coda types and classes. Sperm whale codas are stereotyped sequences of 3-40 broad-band clicks usually lasting less than 3 seconds in total, which functions are to help maintain group cohesion, reinforce bonds, aid negotiations and collective decision-making. These groups with distinct dialects also interact. To give a particular example, in the South Pacific and the Caribbean, there are six sympatric acoustic clans based on coda sharing, which simultaneously differ in movement and habitat use patterns and in feeding success.

Dialects have been described in sperm whales (Physeter macrocephalus) (Picture: CBC News).
Dialects have been described in sperm whales (Physeter macrocephalus) (Picture: CBC News).

ORIGIN OF DIALECTS IN CETACEANS

A recently published article in the magazine Nature suggests a mechanism that may explain the origin of multilevel societies in sperm whales. As we have seen, it is in these societies where dialects are present in cetaceans. So, here we will explain the origin of multilevel societies in sperm whales as an example.

In sperm whales, the upper level of the multilevel society are clans of individuals that communicate between them using similar codas. These clans are originated from cultural transmission via biased social learning of codas, when they learn the most common codas (conformism) from behaviourally similar individuals (homophily). Thus, the result are groups with increasingly homogeneous behaviour with a strong integration. The cultural transmission plays a key role in the partitioning of sperm whales into sympatric clans (clans that live together but without interbreeding). So, it is in these clans where distinctive behavioural patters may appear, like dialects. The lower level, social units, are originated from ecological, cognitive and time constraints and benefits.

Multilevel societies (Picture: Marc Arenas Camps).
Multilevel societies. Individuals (stars and filled circles) are the lowest level and in association (black lines) with other individuals they constitute social units (empty black circles). Socials units with acoustic similarity (orange lines) form vocal clans (blue and green). It is in vocal clans where dialects can emerge (Picture: Marc Arenas Camps).

HUMPBACK WHALES: A DIFFERENT CASE

The differences in the songs of humpback whales (Megaptera novaengliae) cannot be considered dialects since they happen between geographically isolated populations. Due to a geographic and reproductive isolation, these differences have appeared as a result of genetic distinctions among populations.

REFERENCES

  • Cantor, M; Shoemaker, LG; Cabral, RB; Flores, CO, Varga, M & Whitehead, H (2015). Multilevel animal societies can emerge from cultural transmission. Nature Communications. 6:8091. DOI: 10.1038/ncomms9091
  • Conner, DA (1982). Dialects versus geographic variation in mammalian vocalizations. Animal Behaviour. 30, 297-298
  • Dudzinski, KM; Thomas, JA & Gregg, JD (2009). Communication in Marine Mammals. In Perrin W, Würsig B & Thewissen JGM (edit.). Encyclopedia of Marine Mammals. Academic Press (2 ed).
  • Ford, JKB (2009). Dialects. In Perrin W, Würsig B & Thewissen JGM (edit.). Encyclopedia of Marine Mammals. Academic Press (2 ed).

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How do whales communicate with each other?

The post of this week talks about baleen whale communication, it is, cetaceans that feed thanks to the presence of baleen plates in the mouth. In concrete, we will focus on the acoustic communication in baleen whales and, in specific, in the humpback whale case.

INTRODUCTION

Bradbury and Vehrencamp defined the term communication like the process in which an information is given through a signal from a speaker to a receiver and this receiver uses this information to decide how to respond or if the receiver responds to the signal.

There are several types of communication among marine mammals, either chemical, visual, tactile or acoustic. Due to solar light has a delimited capability to penetrate into the water, whales and other marine mammals have difficulties on visual communication with each other from a certain distance, so they use sound. In addition, chemical communication is not efficient in the aquatic environment.

COMMUNICATION PROCES IN BALEEN WHALES

Production and reception of sound

While anatomical structures related with the production and transmission of sound have been found in odotocetes (cetaceans with teeth), they have not been found in the case of baleen whales (mysticetes). Baleen whales, despite they present larynx, don’t have vocal chords. However, it is accepted that cranial sinuses, empty spaces in the skull, are involved in phonation, but its role is unclear.

The big whales are by far the most resounding marine mammals. Humpback whales (Megaptera novaeangliae) produce songs that last some hours and can be heard long distances (some kilometres). Blue whales (Balaenoptera musculus) and fin whales (Balaenoptera physalis) don’t fall behind: they produce low frequency sounds that travel more than 3,200 km of distance. In fact, blue whales produce sounds around 190 decibels, the loudest sound produced for an animal.

La balena blava (Balaenoptera musculus) pot generar sons de fins a 190 db (Foto: iTravel Cabo).
Blue whales (Balaenoptera musculus) can produce sounds of 190 decibels  (Picture: iTravel Cabo).

Some behavioural studies have demonstrated that all cetaceans, but specially odontocetes, have a good hearing.

Function

While some experts defend the idea that this sounds are used to communicate each other at long distances, other suggest that are used to detect the underwater relief to orientate (echolocation). Anyway, it is more accepted that they have a communicative function, including behaviours like exhibition and the establishment of the territory, among others.

THE CASE OF HUMPBACK WHALES

Humpback whales (Megaptera novaeangliae) produce complex sounds that can be heard to long distances. They are one of the most resounding baleen whales. During winter, in the breeding grounds, these whales produce long and complex songs at the same zone. These songs are different in the different zones. These songs (you can hear one of them here) lasts 10-15 minutes, but they can sing them for hours, and are composed by themes, phrases and subphrases. Each subphrase lasts some seconds and are composed by low frequency sounds (normally under 1,500 Hz).

Estructura del cant de les balenes de gep (Megaptera novaengliae) (Foto: Hawai's Marine Mammal Consortium).
Structure of a humpback whale song (Megaptera novaeangliae) (Picture: Hawai’s Marine Mammal Consortium).

But the complexity doesn’t end here. The structure of this musical pieces changes along winter. Not only they change the frequency and duration of the phrases and themes, but also some of them are changed by new compositions. Moreover, they also modified the composition and sequence of these themes.

Anyway, all the whales at the same area sing the same song and all of them modify it at the same rate to other mates. So, they learn from other mates.

Some studies highlighted that adult males are the only that produce this songs. So, it indicates that this songs play a role in reproduction, similar to bird songs. Therefore, these songs indicate to females the sex, the species, the position and that he is ready to compete with other males and he is ready for mating.

In addition, according to Mobley y Herman (1985) the fact that males sing at the same time stimulates the synchronization of the ovulation of the females.

El cant simultani dels mascles estimula la sincronització de la ovulació de les femelles de balena de gep. (Foto: Yellowmagpie).
The fact that males sings at the same time produce the synchronization of the ovultion of females of humpback whale (Picture: Yellowmagpie).

REFERENCES

  • Berta A, Sumich J & Kovacs KM (2006). Marine mammlas. Evolutionary biology. Ed. Academic Press (2 ed)
  • Day (2008). Guía para observar ballenas, delfines y marsopas en su hábitat. Ed. Blume
  • Perrin WF, Würsig B & Thewissen JGM (2009). Ed. Academic Press (2 ed)
  • Reeves RR, Stewart BS, Clapham PJ & Powell JA (2005). Guía de los mamíferos marinos del mundo. Ed. Omega

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Homosexuality is so animal

Fortunately for LGTB collective, greater and greater countries and societies understood that homosexuality is something natural and that it is not an illness. Anyway, despite this is true, it is also true that it is necessary to work hard to achieve equality on lesbian, gay, transexual and bisexual rights and to eradicate the false belief that homosexuality is unnatural. In the next weeks, in cities all over the world like Barcelona and Madrid will take place LGTB Pride parties. For this reason, this article hope to show clear examples that homosexuality is not exclusive of human, but present in many animals. So, there is no reason to continue believing in the argument that homosexuality is unnatural! 

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INTRODUCTION

Homosexuality is a fact present in many animal species. In fact, it has been documented in 1,500 of the more than 1 million described animal species (Bagemihl, 1999). Without going any further, a study of the California University demonstrated that in all the analysed species there were some individuals with homosexual traits or behaviours, including worms, flies, birds, dolphins and chimpanzees, among others.

In the animal kingdom, the concept “homosexuality” refers to any sexual behaviour between same sex animals, like copulation, flirt, mating, genital stimulation and young breeding. In the case of humans, it is more complex than this because there is much more factors and feelings are involved in this.

From the biological point of view, it is supposed that the goal of any species is its perpetuation. So, which is the function of homosexuality? There are many theories about it and they are not particular because for each species there is one explanation or another. Let’s explain three of them! Marelen Zuk, professor in biology at the University of California, propose that not producing their own offspring, homosexuals could help to breed and take care of their relatives, what also contributes to genetic pool. According to the biologist and phsycologist Janet Mann from the Georgetown University, it is a way of creating links and alliances between individuals. Finally, in the case of fruit fly and other insects, the evolutionary biologist Nathan Bailey suggest that the reason of their homosexuality is the lack of the gene that let them to distinguish between both sex. There is also the possibility that homosexuality doesn’t have any function. At any rate, homosexual behaviour may have evolutionary consequences, but it is still being studied.

PINGUINS

On February 2004, New York Times published that Roy and Silo, two male chinstrap penguins (Pygoscelis antarctica) from the Central Park Zoo, coiled their necks, vocalized one to other and had sex. When they were exposed to females, they rejected them. Moreover, zookeepers gave them a fertile egg in order they incubate them and when the little penguin was born they feed her until she was able to live by herself. This is not an isolated case because it have happened more in this and other zoos, like in Bremerhaven Zoo (Germany), Faunia (Spain) and Dingle Ocean World (Ireland).

But this is not exclusive of captive animals. A research done on Adélie penguin (Pygoscelis adeliae) found homosexual behaviours in some of their young individuals. Another research was carried on king penguin (Aptenodytes patagonicus), in which it was observed that 28.3% of males flirted with other males. The reason in this case seems to be an excess of males or high testosterone levels. Anyway, it was found two partners (male-male and female-female) in which one knew the vocalization of the other.

Los pingüinos son un claro ejemplo de aves con comportamientos homosexuales (Foto de Listverse).
Penguins are a good example of birds with homosexual behaviours (Picture from Listverse).

BONOBOS

The bonobo (Pan paniscus), apes very close to humans, are a good example of homosexual behaviours. They are so sexual. It has been observed that, in captivity or free, half of their sexual relationships are with same sex animals. In addition, females have sex with other females almost every hour. The main function of this is to strengthen links between animals. In the case of males, in order to reduce the stress after a fight, a penis fight takes place, that consists on rubbing their genitals together.

En los bonobos, las relaciones con seres del mismo sexo podrían servir para hacer los vínculos más fuertes (Foto de BBC).
In bonobos, same sex relationships may be done to strengthen social links (Picture from BBC).

KILLER WHALES

Homosexual interactions between male killer whales (Orcinus orca) are an important part of their social life. When resident groups join together during summer and autumn to feed, males show flirting, affectionate and sexual behaviours between them. Normally, interactions take place one to one and lasts for an hour, but it can be longer. In this interactions, they caress, chase and carefully push one to the other. Another amazing behaviour is the beak – genital orientation, but it also take place between males and females. Just under the water surface, one male swims in an upside down position, touching the genital zone of the beak. Then, they dive together in a double helix spiral. This happens several times, but they interchange their positions. It is not strange to see them with the erected penis during this interaction. Despite it happens in all ages, it is specially abundant in young animals.

Las orcas (Orcinus orca) son cetáceos con comportamientos homosexuales habituales (Foto de WorldPolicy)
Killer whales (Orcinus orca) are cetaceans with homosexual behaviours (Picture from WorldPolicy)

GUPPIES

A research made on guppies (Poecilia reticulata) demonstrated that the lack of females in the environment during a long period of time produce that males prefer other males even when there are females in the environment. Not only this. When males that had been with females during a long period of time are deprived from females for a short time (two weeks) they prefer males instead of females.

Los machos de guppy preferían otros machos cuando no había hembras en su ambiente durante largos períodos de tiempo (Foto de GuppyFish).
Male guppies prefer other males when there is no females in the environment during a long period of time (Picture from GuppyFish).

DRAGONFLIES

Some studies lay bare that there is a high rate of mating between same sex individuals in dragonflies. The reasons could be the lack of individuals of the other sex or that female tricks to avoid sexual advances of males could produce that males look for same sex individuals. One specific example is blue-tailed damselfly (Ischnura elegans), in which 17% of males of wild populations prefer male partners.

Los machos del cola azul (Ischnura elegans) prefieren a otros machos cuando son alojados en ausencia de hembras (Foto: L. B. Tettenborn, Creative Commons).
17% of male blue-tailed damselfly (Ischnura elegans) prefer other males (Picture: L. B. Tettenborn, Creative Commons).

SOME EXAMPLES MORE

  • Studies on wild occidental gull (Larus occidentalis) show that between 10 and 15% of females are homosexual. It has been seen that they show flirting rituals between them and that they set nets together. They only copulate with males to produce fertile eggs, but then go with their initial partner.
  • On domestic sheep, 8% of males from a flock prefer other males despite the presence of females. But this could benefit other males because they can present the same genes and pass to next generation. But this also benefits females by doing them more fertile.
  • The king of savannah, the lion, also have homosexual behaviours. It has been observed wild male and female lions with this behaviour, include mating.

  • In some species of seahorse, homosexual behaviours between females are frequent, more than heterosexual.

CONCLUSION

Homosexual behaviours are no only in humans, but they are more complex in people. The reason that lead to the development of these behaviours in animals are several: lack of females, to stablish harder links… but there are some examples in which the behaviour is permanent. Moreover, it has been seen that this behaviours are not artificial due to the captivity of animals, like humans in prison, but they haven in wild animals too. So, homosexuality happens in many animals and cannot be considered unnatural. In addition, if it is the result of natural forces it cannot be considered immoral. 

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REFERENCES

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