Last chance to see…the other Yangtze cetacean

“‘Well, we might at least see a finless porpoise,’ he said.

‘They’re not as rare as the dolphins, are they?'”

Almost a quarter of a century after Douglas Adams alerted the world to the plight of the Yangtze’s critically endangered baiji, declared extinct just seven years ago, it appears Asia’s longest river is on the brink of losing its sole remaining cetacean. The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), a distinct subspecies of the narrow-ridged finless porpoise, is under threat from the same factors that led to the extinction of the baiji: extreme habitat degradation, fragmentation, and unacceptable levels of by-catch.

Several steps have been taken to promote the conservation of the porpoise, most notably the creation of seven nature reserves – including two ex-situ reserves designed to maintain reservoirs for replenishment of the river population – and the implementation of a 3-month annual fishing ban. Despite this, the population has been in continuous decline since the 1980s. The population is estimated to have plummeted from over 2500 in 1991 to less than 1300 in 2006. However, this worrying demographic trend is accelerating, with optimistic estimates predicting the extinction of the subspecies within the next century.

The prediction of looming extinction has this month received some ominous support, following the publication of the results from a 2012 census of the Yangtze finless porpoise population. The report estimates around 500 porpoises remain in the main stem of the river, suggesting a more than 50% population decline in just 6 years – compared to the 15 years taken for the population to halve from 1991-2006. This represents an order-of-magnitude increase in rate of decline in the past 20 years, far greater than any of the previous predictions of population decline.

At the current rate, it is likely this subspecies of porpoise will be extinct within the next 20 years, despite current conservation efforts (however limited). At the forefront of these efforts has been the creation of two ex-situ populations of porpoise in lakes connected to the river. It was hoped these populations would buffer the risk of rapid decline through steady immigration into the river. This buffer, however, seems to be also dwindling, with the two lake populations decreasing and gene flow into the river population from these populations  appearing to have stagnated. This lack of connectivity is further compounded by increased shipping activity in the channel connecting one of the lakes to the river, effectively inhibiting migration.

It is clear that current efforts are insufficient to successfully conserve the Yangtze finless porpoise. Yet, in a region where biodiversity takes a back seat to economic priorities, it is unclear how much China is willing to invest – and sacrifice – to ensure the cetacean’s survival. The authors of the report recommend several measures that need to be taken to improve the porpoises chances of survival, including the revision and extension of the reserve network to promote connectivity, the creation of additional ex-situ reserves, and a whole-year fishing ban.

Given China’s track record on conservation issues in the Yangtze, it is unlikely these recommendations will be enforced with much gusto. Consequently, the Yangtze appears destined to lose both cetacean species within less than half a century, with its critically endangered alligator and sturgeon following closely behind.


Mei et al. 2014. The Yangtze finless porpoise: On an accelerating path to extinction? Biological Conservation 172:117-123.

 

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The wild nature of Us

It has been brought to my attention by several people over the past seven-or-so years that the consideration of modern humans as ‘wild’ animals is not ubiquitous amongst ‘learned’ individuals. The answer to this – whether or not humans can be considered truly ‘wild’ animals – appears to me to be an obvious one, and I herein provide the reasoning underpinning my stance on the issue. First, however, it is important to address what one actually means by ‘wild’. Merriam-Webster defines it thus: “living in a state of nature and not ordinarily tame or domesticated.” However, to remove all ambiguity, a more precise definition is required. For humans as a species to be considered wild they must possess the same natural history characteristics shared by all other wild animals, and possessed in their entirety by no domesticated stock, namely: freedom of choice; risk of death – by disease, accident, or at the hands of another organism; freedom of mate choice; responsibility for one’s acquisition of vital resources.

Perhaps the most common argument proffered in support of the ‘domestic human’ position is this: “the extent to which humans can – and do – alter their habitat means they are disconnected from the wilderness, thus cannot be considered ‘wild’.” That this argument is invariably presented at some point during the discussion indicates the proponent has not given the subject much thought. It is undeniable that humans have altered the world around them on a scale unrivalled by any other species, but the habit of altering one’s immediate surroundings to become more conducive to survival and efficient living is not limited to humans. Though it is true we do not stumble across chimney-topped cabins built by mice, the construction of a ‘home’ of one sort or another is a widespread behaviour observed in numerous animal groups, from insects to birds to snails. Perhaps the most notable non-human ‘home’ is that of the beaver. The lodge and associated dam constructed by a family of beavers can in no way be considered a simple manipulation of the environment; the dam – built from mud, stone, and severed branches – serves to flood the immediate upstream area, allowing the beavers easier access to food and providing protection from predators such as wolves. The lodge is equally impressive, a large mass of impregnable timber and mud that rises from the water, the interior of which is accessible only through underwater entrances. Inside the lodge there are typically two dens, one for drying off upon entrance, and a second for living in – separate ‘rooms’ for different purposes!

Architectural wonder is not limited to mammals, or even vertebrates. Certain species of termites have even evolved to grow and maintain ‘home comforts’ within their nests; some species create nests that are constructed in such a way to maintain a constant temperature optimal for cultivating a fungus food source within the nest. The wondrous feats of civil engineering achieved by such lowly creatures as beavers, with their partitioned living-quarters in their vastly modified environments, and termites, with their fungal refrigerators, highlights the weakness of the argument that the human home forms an unnatural barrier between them and the ‘wild’. The ‘home’ is a creation that has provided protection from predators and from the elements, provided a food-store and a place to rear young, since before the evolution of mammals, let alone the advent of civilised man. That the human home appears so much more complex – with its electricity, hot water, and excess – than the seemingly primitive creations of ‘lesser’ animals is subjective. Beavers use timber, mud and stone to build a lodge, as this is their currency; they build with their forepaws and teeth as those are their primary utensils, bestowed upon them through natural selection. In a completely analogous manner, humans use their currency – money and industrially-harvested natural resources – to produce homes designed and built using our primary tools: intelligence and dexterity.

The ‘extended phenotype’ of humans extends beyond the four walls of the home, to infrastructure and technology. Though our tendency to transform wherever we inhabit to improve our living standards seems counterintuitive to being ‘wild’, if one retains the idea of our evolutionarily-produced tools and abstract ecological currency, it becomes clear that our advances in these areas are a natural consequence of our intelligence and analogous to ecological innovations of other species. Birds use thermal currents in the atmosphere to improve journey efficiency; humans use cars, boats and aircraft. Spiders build intricate webs to improve foraging efficiency; humans use weapons. Termites grow and harvest fungi; humans use agriculture. The parallels are endless and highlight one fact: humans are the ‘Jack of all trades’, and exhibit ecological innovations already widespread in nature. Yes, our footprint on the planet is large, but so is that of plants. The oxygen you breathe is a product of simple processes conducted inside plant cells, and has been instrumental in altering the planet to such an extent to facilitate the evolution of an entire Kingdom of organisms, including us. All organisms exert a footprint on the Earth. Some are imperceptible, some instrumental, all are advantageous to the individual producing the footprint. The human footprint is nothing peculiar and, when viewed in a biological context, reinforces the argument that humans are still inescapably ‘wild’.

The next most-common, and equally erroneous, argument goes: “humans have jobs, and money, and buy food from supermarkets, and go to nightclubs to consume alcohol. Such frivolities and removal from the process of gathering one’s food cannot be considered ‘wild’ behaviour.” However, when viewed from an evolutionary perspective, this argument appears rather asinine. As has already been discussed, all organisms depend on a specific ‘currency’ to aid in their quest to fulfil their maximum potential reproductive success. Typically, this currency is food and other natural resources such as suitable habitat in which to rear young efficiently – also known as a territory, home range, or even a ‘home’. As humans have mastered the techniques of agriculture, food storage and safe homes, a more abstract currency has been developed to maintain the requirement of individual effort to acquire important resources: money. Although no system is perfect, the human currency system tends to reward more ‘successful’ individuals – in terms of job positions, level of education, and even physical appearance – with more money than less successful individuals. Thus, more culturally successful people have more currency (money), to invest in good food, safe homes and other resources (cars, gifts), signalling their reproductive quality to a potential mate.

As with the role of currency in human society, nightclubs and other social gathering have their purpose firmly rooted in the evolutionary goal of reproductive success. Research has suggested the behaviour of male humans in bars and nightclubs is similar to that of lekking birds. As in avian leks, male humans appear to distribute themselves in establishments in a way to optimise their visibility to potential mates. Further, reproductively fitter males – i.e. individuals with greater physical appearance and/or monetary wealth – occupy the most conspicuous, and therefore most optimal, areas of a club or bar. The physical quality of a male to a female can be, and has been, examined thoroughly. For example, individual females vary their taste in men during the menstrual cycle; ovulating females are attracted to ‘masculine’ men, while menstruating females are increasingly attracted to more ‘feminine’ men. This is likely due to the signalling quality of different male physiques – more masculine men are likely to provide fitter offspring, so should be mated with during ovulation, whereas more feminine men are likely to form a strong bond with the female, thus it is beneficial to begin a relationship with feminine men outside of ovulation, to allow a bond to form prior to pregnancy. The two strategies offer differing advantages and disadvantages; feminine men may not provide offspring to the same quality of progeny born to masculine men, but are more likely to provide the female with resources and parental investment for a greater period of time, increasing the potential successful development of the offspring. Conversely, a masculine man is likely to provide a higher quality offspring, so the loss of parental investment experienced by his desertion is offset by the quality and potential survivability of fitter offspring. That such complex mating strategies still exist in human societies, however subtle and imperceptible they appear to the individual at the time, indicates free mate choice is still an integral component of human society and, ultimately, evolutionary biology.

Though the existence of ‘free-will’ is currently subject to much debate between philosophers and scientists alike, that we as humans are free to make choices is undeniable; an individual is free to do as they wish, to travel where they wish, to behave as they wish, and is constrained only by their wealth and knowledge of the effects of their behaviour on their future reproductive success. For example, an individual knows one is free to murder, yet is also aware of the negative impact of imprisonment has on one’s future reproductive fitness. That we face retrospective punishment for certain actions is not a strictly human and non-wild concept, and ‘cheats’ in all animal societies are punished by other individuals; chimpanzees are beaten for failure to adhere to group conventions, while a lion will be chased from a meal for not waiting its turn in line. Further, all individual humans are susceptible to death. Murder is not rare, and is even frequent in some human communities, from inner-city USA to rural Africa. Despite the best efforts of medicine, humans are killed by viruses, bacteria, disease, and by accident, at a still substantial rate. They are not shielded from death any more than a rabbit in an area devoid of stoats; there still remains a myriad ways to die other than by stoat.

It is clearly undeniable that humans meet each of the criteria for a species to be considered ‘wild’, thus we should be duly recognised as such, rather than the veritable Homo domesticus we usually consider ourselves to be.

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Corvids: The Avian Equivalent of Primates

Ravens (Corvus corax), and corvids in general, are renowned for their repertoire of ‘intelligent’ behaviour, including tool use and complex sociality. Research published online today describes a previously unknown facet of raven behaviour.

The use of referential gestures, such as holding or pointing to objects to attract attention, has long been considered a skill unique to humans and our closest relatives, the great apes. However, such behaviour has recently been observed in ravens. This is not the first instance of ravens exhibiting cognition to rival non-human primates (Prof. Jerry Coyne has a great piece, with videos, here).

The paper, in Nature Communications, describes the use of ‘referential gestures’  in wild ravens (Corvus corax), and the affiliative interactions induced by such behaviour. The authors observed ravens performing two distinct behaviours – ‘showing’ and ‘offering’. When ‘showing’, ravens picked up inedible items (such as moss and twigs) in their beak, with head tilted upward, and remained in this position to display the item to a conspecific. ‘Offering’ behaviour consisted of presenting an object in much the same way as when ‘showing’, followed by movement of the head up and down repeatedly. Such behaviour was always directed toward a recipient, and elicited a response in 100% of observations – the vast majority of which were affiliative (i.e. approaching, billing, mutual manipulation of object).

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The authors hypothesise that convergence on referential gesturing in such unrelated groups as corvids and primates highlights the role of cooperative motives in the evolution of complex modes of communication. Further, if one follows this to it’s logical conclusion, one day we may have talking crows! Another fantastic reason to conserve the biodiversity on our fragile planet.

This discovery, however, is just the tip of the iceberg – the latest of numerous recent findings in animal behaviour that are challenging the notion of the intellectual superiority of primates over other animals. For example, tool use has been observed in numerous birds, a species of dolphin, a fish and even an invertebrate. These examples all serve to put into perspective the nature of those behaviours that, when observed in human-like organisms, are lauded as “intelligent” and “advanced”; they are evolutionary adaptations unlike any other, capable or arising in a myriad species.

Here are my personal favourite videos of less ‘intelligent’ species trivialising ‘complex’ vertebrate behaviour:

‘Tool use’ in a sparrowhawk

Courtship display of the peacock spider

                                                                           

Pika, S., and T. Bugnyar. 2011. The use of referential gestures in ravens (Corvus corax) in the wild. Nature Communications 2:560

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Snake Bite Produces Pain

In a paper published in last week’s Nature, researchers have identified a toxin in the venom of the Texan coral snake (Micrurus tener tener) that directly induces pain in bite victims. The toxin, known as MitTx, has been observed to activate specific signalling macromolecules called acid-sensing ion channels (ASICs). Further, venom from the second coral snake species included in the research (M. frontalis) also activated a similar group of neurons.

What is so interesting about this novel property of snake venom is the ecology of the species from which it is produced: New World coral snakes (genera Leptomicrurus, Micruroides and Micrurus) exhibit aposematic (warning) colouration of varying degrees. Both species in the study possess the red/yellow/black banding typically associated with coral snakes, and the pattern is shared by numerous nonvenomous and mildly-venomous snake species found throughout the entire range of coral snakes, although which group of snakes is mimicking which is poorly understood. However, the discovery of pain-inducing properties of coral snake venom could provide insights into the evolutionary significance of coral snake colouration, and possibly explain the mystery of who is mimicking whom.

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The revered coral snake colouration

If pain-producing toxins prove to be widespread in the venom of coral snakes with aposematic colouration, and absent in closely-related or sympatric venomous snakes that lack such patterns, it would suggest that the bright colours may have evolved as a conspicuous signal for predators to associate with the excessive pain of a coral snake bite. This, in turn, would then indicate that the occurrence of similar colour patterns in less dangerous sympatric snakes is due to selection favouring a resemblance to venomous coral snakes, or Batesian mimicry; the harmless species exploit the capability of predators to recognise the pattern of unpalatable and dangerous species, thus lowering the predation pressure on the harmless species.There are, of course, some potential deal-breakers for this possible explanation to a long-studied phenomenon. As mentioned above, the presence of the toxin in numerous species that do not have aposematic colouration would suggest the evolution of aposematism in coral snakes was not exclusively linked to the possession of a particularly painful bite. Further, the research was in vitro, using the neuronal system of rodents, whereas the natural predators of coral snakes (mainly birds and other snakes) may exhibit different reactions to the toxins.

Either way – whether or not this toxin can provide greater insights into the evolutionary history of one of the most iconic snake colourations worldwide – the presence of such toxins in snake venom raises numerous lines of further research regarding the nature of predator-prey interactions.

                                                                                                     

Bohlen, CJ. et al. 2011. A heteromeric Texas coral snake toxin targets acid-sensing ion channels to produce pain. Nature 479(17th November 2011):410-414.

Image from Wikipedia.

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Curiosity Lifts Off!! (Pun Intended)

As this is my first post I’ll keep it short, but what better time to start blogging my thoughts on the latest activity in science than today? Unless you’ve been hiding under a Martian rock, in which case you will surely see for yourself in around eight months time, you’ll have heard all about NASA’s Mars Science Laboratory (or MSL) launch today (Saturday).The timing of this mission could not be more perfect for NASA and the US scientific community as a whole. Following the decommissioning  of the Shuttle program, the widely-reported financial woes of the James Webb Space Telescope and the humbling use of Russian Soyuz spacecraft to maintain a human presence in space, the USA’s status as leader in all things cosmological has come under increased threat. This ambitious undertaking, paired with the recent failure of Russia’s Phobos-Grunt mission, has the potential to restore the USA’s image as the trailblazer in space exploration. Indeed, if we were still engulfed by Cold War hysteria, a failed Soviet space mission being followed so shortly by an obvious symbol of engineering superiority by the US would have the more skeptical of us calling foul play. However, I digress – let’s return to the MSL.The major component of the MSL is the Curiosity rover, which is intended unravel that mystery of mysteries – an idea which has fascinated scientists and the public alike for over a century – life on Mars. Curiosity is carrying ten times the mass of scientific instruments as any previous rover but, let’s be honest, the most exciting components are the cameras! After the beautiful images beamed back to us by Opportunity, Spirit and the two Viking landers, there is a thirst for more splendid images and HD video footage of the Martian surface.

The main obstacle standing between the secrets of the Martian past and us is the landing; NASA’s trickiest to date. However, if all goes according to plan, the next few years may be the most important – and informative – in the history of our love affair with Mars.

Endeavour crater, Mars

Image from NASA

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