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Lack of phosphorus puts global food security at risk

Phosphorus (P) is an indispensable element for life on Earth. Essential structures for any organism like DNA or RNA contain this element, and plants can not perform photosynthesis without it. Because of this, crops require huge amounts of phosphorus to meet the standards of efficiency and productivity needed to feed an ever-growing human population. However, this is a limiting and finite resource, and the predictions are not promising: reserves will be depleted in about 100-150 years. That will lead to significant geopolitical problems still unimaginable because, apart from the ephemeral nature of this resource, there is the fact that 90% of stocks are in the hands of only 6 countries. Conflict is served.


Anyone who has ever had to buy fertilizer will recognize this sequence: N-P-K (nitrogen, phosphorus, potassium). They are the most used nutrients for gardening and plant production in general. Without them, plants do not grow or can not develop enough to persist in the long term. Of the three main nutrients, potassium is the most abundant in the earth’s crust (representing approximately 2.4% of the earth’s surface by weight), especially in ancient seabed and lakebeds, as well as being the most available for plants. On the other hand, nitrogen in its gaseous form is extremely abundant (78.1% of the air around us is molecular nitrogen), but not their molecules in solid form, which are usually scarce due to their high mobility throughout the soil. However, thanks to the Haber-Bosch process (which lead researchers to win the Nobel Prize in Chemistry), solid nitrogen (in the form of ammonia) was produced from gaseous nitrogen, leading to a high availability of this inorganic fertilizer.

Friz Haber (right) with a scientist who manipulates the Haber-Bosch method. This way of extracting the atmospheric nitrogen and turning it into ammonia is considered, by many scientists and historians, as the most important invention of the modern history. Without it, the world would not have been able to afford even half of the current food demand. Source: el juicio de fritz haber.


Phosphorus, however, is the third party in discordance. Essential for life, it is the main component of DNA, RNA, ATP (the energy used in cellular processes) and phospholipids, which cover cell membranes. It is present in the bones and is involved in almost any animal biological process. In addition, it is imperative for plant growth: without phosphate, photosynthesis can not be carried out. The biggest problem with phosphorus is that it is not free in nature. Plants and, in general, all organisms, satisfy their phosphorus needs thanks, mainly, to another living organism: animals, from plants and, these, from animal residues or their corpses, which release the Phosphate in the decomposition process. In fact, the most important fertilizers until the arrival of inorganic fertilizers, already in the twentieth century, were the excrements and urine of farm animals, which contain a large amount of phosphorus, in addition to the other elements already mentioned. However, as a result of the Haber-Bosch invention and the increase in food demand as a result of population growth, phosphorus deposits, which are in the form of minerals and are actually scarce in the earth’s crust, began to be exploited.

Guano accumulated on an islet of Peru. Guano, together with excrements and urine from farm animals, was an important source of phosphorus until the 20th century. This substrate, formed from continuous depositions of seabirds, seals and bats, is still very much appreciated even today, especially in organic farming. Source: Hiding in Honduras.



Phosphorus is an irreplaceable and non-synthesizable resource. Reserves are finite and are being wasted, since much of the fertilizer applied is not assimilated by plants and, through the soil, ends up in the sea or in the lakes, where they unbalance the ecosystems. Being such a scarce resource, it is often the limiting resource in most ecosystems. For that reason, an overfertilization of phosphorus is often exploited by autotrophic algae to grow uncontrollably, which, in many cases, causes blooms that can generate important animal, economic and environmental losses.

Extension of the vegetation of the Mar Menor (Murcia) in 2014 and 2016. 85% of the vegetation has died in less than two years, due to strong phenomena of eutrophication, in which phosphorus has played a key role. The excess of nutrients allows algae proliferation, which end up causing difficulties of light infiltration which, in turn, preclude phothosynthesis, causing the death of plants. Source: El País.


The United States Geological Survey (USGS) has estimated the world’s reserves of phosphorus at 71 billion tonnes. 90% of these are in the hands of 6 countries: Morocco (where, according to the USGS, 75% of the world’s mineral reserves are found there), China, Algeria, Syria, South Africa and Jordan. However, United States and, specially, China (accounting for 47% of world phosphate production), are the countries that are currently extracting more phosphorus from their deposits. This production has been increasing in the last years, and it will go to more in the coming decades. According to this recent article by Nature, it will be necessary to double, by the year 2050, the use of phosphate fertilizers to meet the demand of food, in a world where there will already be 9,000 million humans. But, by then, more than half of the phosphorus in the reservoirs will have been used. This study warned of the possibility that we were reaching the peak of phosphorus production, although new calculations estimate their peak around the year 2040. In any case, if we continue with the current production, the reserves will be depleted in no more than 100 years.

World phosphate rock reserves by country. Morocco capitalizes on reserves, followed by China and Algeria. Around 90% of the world’s phosphorus reserves are found in Africa, which predicts a future in which this continent will play a very important role in the negotiations for this finite resource. Source: WRForum.


A symptom of the potential shortage of phosphorus in the not too distant future is the rise in phosphorus prices that has been observed recently due to rising demand. Between 2007 and 2008 the price of phosphate tons increased threefold from 2005 values, and cost up to 9 times more than in the 1970s. In addition, it has been estimated that by 2035 phosphorus demand will exceed supply, what will cause an increased prices and, with them, political tensions. No stranger to it, many countries are working on ensuring a supply of this valuable resource for a few more decades. China, for example, which is now the largest producer (what does not mean the holder of the largest reserves) has begun to impose 135% tariffs on its exports. The United States, on the other hand, has signed a bilateral free trade agreement with Morocco, which gives it the rights to exploit their long-term phosphate deposits. Taking into account that most of Morocco’s phosphate reserves are in Western Sahara (a region that has fought for its independence since its occupation in 1975), it is not surprising that the United States has always supported Morocco in the United Nations Security Council, vetoing any proposal in favor of the independence of Western Sahara.

Rise of prices of different phosphate minerals. Prices are expected to rise in the coming decades, as phosphate deposits are depleted. Source: USDA.
Estimation of the evolution of phosphoric rock production and the moment when it will reach the peak of production. Many scientists agree that reserves will last between 60 and 130 years. Source: Cordell et al., 2009.


According to the latest estimates, phosphorus deposits will be depleted, affecting crops around the world. This decline in food production will have a global repercussion, especially in the poorest countries, the most susceptible to a possible decrease in food production. Failing to establish measures to reduce global population, the lack of phosphorus combined with climate change will lead to tense relations between many countries, leading to geopolitical conflicts on a global scale.

According to Metson et al. (2016) a plant-based diet would help to reduce the phosphorus demand. According to their calculations, a vegetarian person requires approximately 4 kg of phosphate rock per year, almost 3 times less than a meat-based diet, which consumes about 11.8 kg of phosphorus per year. Source: Jeremy Keith.

For that reason, the main solution is to use phosphorus in a more rational way and to recycle it as much as possible. Today, around 80% of phosphorus is lost between the exploitation of the mineral, its transport and its application in the fields, which requires us to make a more sustainable use of this resource. However, the world food security will only be able to mantain its production by recycling. The main proposal would be to return to the beginning: to collect human excrets and urine, generated in cities and towns, to recover all that phosphorus that, in other conditions, would end up in the aquatic environment. Approximately 100% of the phosphorus consumed by mankind through food is excreted in excrets and urine. Collecting it would be like a double-edged sword: on the one hand we would satisfy the phosphorus demand of the crops and, on the other hand, we would avoid the eutrofization of waters due to the excess of these nutrients. Furthermore, a change in diet, prioritizing vegetables instead of meat, would reduce the demand of phosphorus between 20 and 45%, according to Cordell et al. (2009). Other solutions include the recovering of the use of manure in more rural and less-technological areas and promoting the composting of food waste in households, factories and commercial establishments. Finally, a waste from wastewater treatment plants, called struvite (magnesium ammonium phosphate) could help to fertilize the fields in an effectively and cleanly way.

Struvite ore, like the one from the image, is obtained spontaneously in sewage treatment plants. Although it causes obstruction problems in the water treatment plant pipes due to its crystallization, it could be used as a clean fertilization system that would provide phosphorus, nitrogen and magnesium. Source: Creative Commons.

The madness begun at the beginning of the 20th century with the exploitation of the phosphoric rock to produce food in great quantity is almost over, and this requires us to adapt our crops and, perhaps, our way of life, to a future that will have to drink a lot of the proceedings carried out in the past. There is a need for a change of mentality, centered on a reduction of the world population and on a major sustainability of natural resources, if we really want to guarantee a world where no one is hungry.


The 5 most threatened species by traditional Chinese medicine

Traditional Chinese medicine has boomed in recent years, thanks to increased purchasing power, especially Chinese Asian middle class. This ancient medicine is based on the concept of vital energy, that invades every corner of the body and organs, and can be acquired through ingested substances, as are parts of various animals. Despite numerous studies, there is no scientific evidence of its benefits to human health. In contrast, there is evidence of an alarming decline in populations of emblematic species such as tigers, rhinos or lions.


3000 years ago emerged, within the Shang Dynasty, a type of medicine that would completely change the life and habits of the Asian people. The basis of traditional Chinese medicine have a strong philosophical component and focus on the concept of ‘Qi’ or vital energy. This energy flows inside the body through channels or meridians, which in turn are connected to organs and bodily functions. The ‘Qi’ regulates the spiritual, physical and emotional balance of the person, and can be altered when the Yin and Yang (negative and positive energy) get unbalanced. This imbalance and alteration of vital energy is what leads to all kinds of diseases.

According to traditional Chinese medicine, there is not a specific disease, but sick people. Treatment focuses on the affected organ or organs and the whole body, in order to try to restore the balance between Yin,Yang and meridians. Source:

Since ancient times, diseases have been fought with many remedies, many of them derived from animals. Almost any Asian species has been used for traditional medicine, such as cows, wasps, leeches, scorpions, antelopes, sea horses, dogs or snakes. Despite the zero scientific evidence of its benefits, its popularity has been increasing with the population explosion and the purchasing power of Asian countries, especially China and Vietnam. Many ‘new rich’ find in these products a way to distance themselves from other social classes and show off their new lifestyle. As a result, many species are in danger of extinction in the coming decades if nothing is done about it.

In this article we will have a look at the 5 most threatened species by Chinese medicine, and the actions that are being carried out to improve their situation.


Tiger (Panthera tigris)

The tiger is undoubtedly the most emblematic and admired animal by traditional Chinese medicine. Practically all its parts has been used, such as its nose, tail, eyes, whiskers, brain, blood and even penis. Each part has been associated with a particular cure. Eating your brain, for example, combat both laziness and pimples, while the eyes are used to treat malaria and epilepsy.

Unlike other animals used for traditional medicine, tiger parts are not only sold to Asian countries like China, Taiwan, Japan or South Korea, but also to occidental countries, even the United States and United Kingdom. In fact, in cities like London, Birmingham or Manchester you can find products that claim to contain tiger bone. The price of tiger bone is between 140 and 370 dollars per kg in the US, while a cup of tiger penis soup (that it is used to increase virility) reaches 320 dollars.

Wine made of Siberian tiger bones. Wine tiger is one of the emerging threats for the species. This bottle costs about 200 dollars and is sold as a luxury product. Source:

Although there are only  3,200 tigers in the wild (of the 100,000 existing a century ago), there are countries that contain tigers as Myanmar, Laos and Cambodia who have not yet signed the CITES agreement, which means that hunting is still legal. In the airport of Hanoi, for example, it is still possible to buy bones, organs and tiger skins without any difficulty.Te

Despite the ban on trade in tiger bones in China in 1993, the business of the tiger is still a very important business in the country. In fact, as pointed out by the researcher and writer Judit Mills in an interview of Yale Environment 360, from that year the number of tiger farms increased rapidly, reaching, at present, the number of 6000 tigers in these places. Most of these farms are dedicated to the growing business of tiger wine, symbol of high status and wealth among the Chinese population. The tigers are fed like cattle until they are killed to extract their bones, which will be immersed in rice wine. The longer they remain in the broth, the higher the price of the bottles.

Just over a month ago, a scandal involving tigers and traditional medicine splattered the Kanchanaburi Tigers Temple in Thailand. In there, more than 40 dead tiger babies were found in freezers, allegedly in order to deal with them on the black market that involves this mythical species.

Baby tigers in jars were found in the Temple of the Tigers, in Thailand. It is suspected that the Buddhist temple is behind a web of illegal trade in tiger parts. The temple has been closed and monks are being investigated. Source: El Mundo.

Asian black bear (Ursus thibetanus) and sun bear (Helarctos malayanus)

Bear bile has been used in traditional Asian medicine for thousands of years. Yore, bile was extracted once the bear was dead, using its meat as well. However, since 1980 the popularity of this product grew, and a flourishing industry was settled and growing year after year. It is estimated that there are currently more than 12,000 bears in farms bile extraction in China and Vietnam.

Bear bile from China is sold in Malaysia. In a recent research conducted by TRAFFIC, of the 365 traditional medicine shops present in Malaysia, almost half of them (175) were selling products containing bear bile. Source: TRAFFIC.

Thanks to its high levels of ursodeoxycholic acid, bear bile can help to treat liver ailments and bladder. However, the extraction of bile causes to bears an unimaginable damage, both physical and psychological. In most cases, bears are confined in cages whose size is like a phone booth, and are continuously sedated so they do not give problems. Poachers make them a hole in the gallbladder and let it drip in order to extract the bile. This heinous practice is still legal in China, although 87% of the population disagrees with this practice.

In many cases the animals are born and grow in the same cage, to the extent that their bodies just outlined by the own cage bars. Many lose much of their teeth by gnawing the bars continuously to try to escape, or attempt suicide punching themselves in the stomach. In this sad picture we see a sun bear in an illegal farm in Malaysia. Source:

White rhinoceros (Ceratotherium simum)

If we look back, it might seem that the situation of the white rhino is excellent. This African species was on the brink of extinction in the early twentieth century, when there were only 100 individuals. Fortunately, thanks to numerous international efforts, the species recovered surprisingly and currently has a population of about 20,000. However, the situation of rhinos is critical again, because of the poachers kill more than a thousand of them every year, which has reignited the alarms for this species.

A woman prepares tea rhino horn in a cafe in Vietnam. Rhino horn ingested in powder form and is very popular in Vietnam. Among other benefits, it is believed to cure cancer. Source:

The rhino (the Asian rhino in that time) has been hunted since the dawn of traditional medicine, as there are records of their hunting since 200 B.C. Horns, blood, skin and even urine have been used since ancient times as a remedy for various ailments such as nosebleeds, strokes, seizures and fever. Today, the main goal is his horn, which reaches exorbitant prices on the black market. A rhino horn can reach up to 46,000 euros per kilogram on the Asian black market, which has already been exceeded the price of gold. The business has prospered thanks to this great incentive, the ease of hunting these animals (they are slow, nearsighted and docile) and the lack of vigilance in the countries they live. The main destination for rhino horn is Vietnam, where the belief in their properties is stronger.

South Africa is by far the country that has more white rhinos (around 90%) and the most affected by illegal hunting. In recent years, hunting has suffered an alarming increase. It surprises and scares simultaneously when comparing the only 13 deaths in 2007 with the nearly 1200 deaths occurred in 2015. Source: TRAFFIC.

Pangolin (family Manidae)

Probably, the hunt that has increased more in recent times is the pangolin hunting, especially in China and Vietnam, its main markes. They are hunted for their meat and scales, wich are used for traditional Chinese medicine as a remedy for all kinds of diseases: malaria, anziety,depression, asthma and even cancer. Of course, scientific investigations have found no evidence of health benefits, and it is very unlikey to occur, because their scales are made of keratin, the same material that forms our fingernails and hair, or rhino horns.

Pangolin scales for sale in Mong La, a tourist city in Myanmar and one of the msin focus on illegal sale of animal parts. One kg of pangolin can be paid at 175 dollars on the black market. Source: TRAFFIC.

Much of the hunted pangolins come from Myanmar, a country that has become, unfortunately, a gateway for most hunted pangolins in Asia or Africa. According to TRAFFIC, in the period from 2010-2014 were seized, only in Myanmar, 4339 kg of pangolin scales and 518 dead bodies. In the Philippines, in April 2013, a fishing boat containing 10,000 kg of pangolin scales was seized, which amount of 20,000 to 25,000 pangolins. With a population in continuous decline, the situation is far from improving. It is no wonder: a hunter, which in many cases has enough to survive, can gain up to 1,000 euros for just a single pangolin.

Pangolin scales can be prepared and consumed in many different ways, either fried, dried or served with vinegar or sauces. In addition, it is believed that his blood and embryos (as the photo) cure sexual impotence. Source: National Geographic.

Lion (Panthera leo)

Lion has been the latest to join this unfortunate list. It was once one of the most abundant larger cats on the planet, with an estimated population of more than 400,000 individuals in 1950. Nowadays, it is calculated a population of no more than 20,000 individuals, a fact that has placed them in the Red List species in the Vulnerable category.

Lion bones placed in the sun to dry them. Once they are dry, they will be sent to Laos and Vietnam, where they will be pulverized. A skeleton as above can be cost 75,000 dollars. Source:

Although the greatest threat for the lion is still habitat loss, the increase of protect measures for tigers in Asia and their low number has placed the lion as a new target for the mafias, as indicated in this 2015 Nature article. In 1995 it was documented for the first time the use of parts of lion in traditional medicine, when it was discovered several typically tiger products containing lion parts. In December 2009 the CITES agreement allowed the export of skeletons lion to Asia. It is estimated that from that date until the end of 2011 more than 1160 bodies of lions were exported, mostly to Laos and Vietnam. The main use of lion bones is to serve as a substitute of tiger bones as a sexual enhancers.

It is very easy to find products made with bone lion online. Get prices and easy ways to buy online did not cost me more than two minutes. These products, in particular, promise to lengthen the penis and improve sexual potency. Source: Male-sexenhancement.


  • Tiger: Many Asian nations such as China, Nepal, Japan, South Korea and Thailand have pledged to enact laws that prohibit trade of tiger products, preserving their habitat and form a regional network to stop the tigers trade. Hong Kong, which accounts for almost half of exports of tiger parts, has intensified controls, while Taiwan, thanks to a recent trade control law, conducted numerous seizures, arrests and extensive searches for illegal tiger parts.
  • Asian black bear and sun bear: By mid-2015 it was known that an important pharmaceutical Chinese was working on an alternative synthetic product for bear bile. This product could finally end up with the bear bile farms. However, it is still necessary the total abolition of this practice in China.
  • Rhinos: There is a strong debate about legalizing rhino horn trade in South Africa. Some NGOs believe that this would lead to a fall in prices on the black market, while others argue it would raise the demand and mafias would still control the market. TRAFFIC along with Save the Rhino International launched an awareness campaign in Vietnam to persuade consumers of rhinoceros horn to reject its use. In addition, TRAFFIC got the commitment from the Association of Traditional Medicine of Vietnam to promote the reduction of demand of rhino horns.
  • Pangolin: Trade with pangolins and parts is protected by law in Myanmar, the most affected country by illegal trade. In addition, Asian pangolins are included in Appendix II of CITES, which means that international trade is prohibited. China is increasing control of smuggling pangolin, and has already imposed tough penalties to pangolin traffickers.
  • Lions: They are listed in Appendix II of CITES, which means that trading of its parts is strictly controlled. Farms created for lion hunters are the main supply of bones for Chinese medicine, that means that, for now, this phenomenon is having little impact on wild populations.



Reasons to watch marine mammals in captivity (or maybe not)

The topic we are discussing this week is marine mammals in captivity, a very controversial subject. While some people totally agree with this practice because they defend that are beneficial (not only economical), others are against it.


In the discussion about marine mammals in captivity; zoos, aquaria and and dolphinaria maintain that their shows have such a great value in conservation, people learn a lot and that marine mammals have a good life. On the contrary, animal protection groups and more and more scientists defend their lives are impoverished, people don’t receive a good information of the species and that captures of wild animals negatively impacts populations and habitats.


Despite in some countries is compulsory to offer educational values in their shows, there is less evidence that the industry spreads information about marine mammals and their habitats. There are more than 1,600 centres in United States and just a negligible part are actually involved in educational and conversational issues, since most of them just aspire to entertain their visitors.

Tricks performed by sea lions, dolphins or whales are exaggerated variations of their natural behaviours and cause the audience loose the notion of the place they are: inside pools confined by Plexiglas. In a survey of 1,000 US citizens, the respondents overwhelmingly preferred to see captive marine mammals expressing natural behaviours rather than performing tricks and stunts.

Killer whale and Sea lion - Daniel BianchettaContrast of the behaviour between a killer whale (Orcinus orca) and a sea lion. In the right, the natural behaviour, which consists on a killer whale capturing a sea lion (Picture: Daniel Bianchetta). In the left, artificial behaviour in which a sea lion gives food to a killer whale.

In general, almost nothing is explained  about natural behaviours, ecology, demographics or population distribution during the shows. In addition, it has been demonstrated that the information is sometimes incorrect of distorted. For example: SeaWorld doesn’t use the word “evolution” as many visitors consider the theory of evolution to be controversial, they fool in the explanation of the drooping fin syndrome in killer whales or about their life span in captivity.

Another example is that many actions performed by dolphins in shows or observed being directed toward visitors or trainers that are portrayed as play or fun (such as the rapid opening and closing of the mouth and the slapping of the water surface with the tail flukes or flippers) are actually displays that in wild animals would usually be considered aggressive.

Tail slapAggressive behaviour of a dolphin, slapping the water surface with the tail flukes(Picture from Sara's Cetacean Stories).

So, the exhibition of marine mammals does exactly the opposite of what the industry rhetoric claims: instead of sensitizing visitors to marine mammals and their habitats, it desensitizes humans to the cruelty inherent in removing these animals from their natural habitats and holding them captive.


Zoos, aquaria and dolphinaria have increasingly promoted themselves as conservation centres, emphasizing their role as Noe ark. In fact, they do no more than produce new individuals of a limited group of species and do not maintain true conservation programs.

While several zoos have programs to breed endangered species in captivity with the intention that these animals be used in restocking depleted populations, this is not the case with dolphins. Only one facility attempted a captive breeding program for baiji or Yangtze river dolphins (Lipotes vexillifer).

Baiji-at-waters-surface-to-breathe-showing-blowholeBaiji or Yangtze river dolphin (Lipotes vexillifer) (Picture: Mark Carwardine, Arkive).

Moreover, the number of centres that invest money in conservation programs are few in number and the amount of money is less that 1% of their benefits. Fewer than 5 to 10 percent of zoos, dolphinaria and aquaria are involved in conservation programs, either in natural habitat (in situ programs) or in captive settings (ex situ).

Nevertheless, in Europe these centres are obliged for law to develop conservation programs to free the animals breeding in captivity to the nature. The truth is that the overwhelming majority of marine mammal species currently being bred in captivity is neither threatened nor endangered. In addition, the success of these programs would be in the capability to introduce the animals in the nature, what has been done in few chances.

What is worse is that many dolphinaria and aquaria are buying animals directly captured in the wild populations.


All cetacean capture methods are invasive, stressful and potentially lethal, despite the method generally considered the better consists on chasing them by small boats and then herded together and encircled by a net. The process is so traumatic that mortality rates shoot up six-fold in the first five days of confinement. The dolphins not selected and released from the net may experience a similar risk of dying once the capture operators have left the area.

japan-environment-dolphinsCapture of dolphins in Japan during a seine-net capture (Picture: Adrian Mylne, Reuters)

The most violent and cruel method of collecting cetaceans for dolphinaria is the drive fishery, used primarily in Taiji and Futo, Japan. A fleet of small ships produce underwater noise with metal pipes to force the dolphins to go into shallow water. Some of the animals are set aside for the public display facilities, while the rest are killed for human and pet food and other products.

Peter Carrette Archive CollectionDolphin slaughter in Taiji (Japan) (Picture: unknown author).


The one area of activity in which dolphinaria and aquaria can legitimately claim to serve a conservation function is work involving rescue, rehabilitation and release of stranded marine mammals. Indeed, there are some very good stranding rehabilitation programs, but the interests are not always clear.

Usually, the real interest is to promote a good reputation of themselves, so they promote themselves as altruists centres that care for marine mammals in the wild. In addition, they use a stranding as proof that marine mammals’ natural habitat is a dangerous place full of human-caused and natural hazards. The public receives a skewed picture in which an animal’s natural environment is hostile and captivity is a benign alternative.

Also disturbing is the fact that these industries appear to evaluate each animal in terms of display potential. Species that are highly desirable or rarely observed in captivity may be determined to be unsuitable for release.


Almost always, dolphinaria and aquaria claim that they foster research and scientific study of marine mammals, thereby contributing to both education and conservation. However, much of what can be learned from captive marine mammals has in fact already been learned (reproductive physiology length of gestation, visual acuity and general physiology). Moreover, most of the results given by studies made on captivity animals have been demonstrated to not be correct, specially those related with behaviour.

There may be some research questions that the study of captive animals can answer most directly, but due to advancements in technology such as biopsy darts, electronic tags and underwater video, as well as improvements in capture and release techniques, it can be studied in wild animals.

sea-lion-metabolic-domeUse of a metabolic dome to study the metabolism of sea lions (Picture from Vancouver Aquarium).


  • Kleiman, D.G.; Thompson, K.V.; & Kirk Baer, C. (2010) Wild Mammals in Captivity. Principles and Tecniques for Zoo Management. The University of Chicago Press (2 ed).
  • Rose, N.A; Parsons, E.C.M & Farinato, R. (2009). The case against Marine Mammals in Captivity. The Humane Society of the United States and the World Society for the Protection of Animals (4 ed)

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