Some new papers have come out from both the Pied Babbler Project and the Arabian Babbler Project. I’ve put the abstracts and links below. This is a very quick blog, basically trying to get people to read these two great papers.
 
The first is Sabrina Engesser’s work into vocal communication and syntax in pied babblers. Using observations and playback experiments, Sabrina has been able to show that the order in which alarm and mobbing calls are given is highly important for these group living birds. Syntax is something that humans use and has been observed in primates but never in birds. This ground breaking work is important for understand how language may have evolved and how widespread some of the components of our communication are in the natural world.
 
The second is from Oded Keynan, this time looking at population dynamics instead of his normal social learning research. This new work shows that the group living Arabian babblers suffer the population and group effects of the Allee effect. Larger groups are better able to rear young and persist than smaller groups, and this isn’t just on a group level but also denser populations do better as well. Interestingly, however, immigration and emigration don’t really have an effect.
 
I hope you have a read, because they’re two great bits of research.
 
Meaningful call combinations and compositional processing in the southern pied babbler. PNAS
Language’s expressive power is largely attributable to its compositionality: meaningful words are combined into larger/higher-order structures with derived meaning. Despite its importance, little is known regarding the evolutionary origins and emergence of this syntactic ability. Although previous research has shown a rudimentary capability to combine meaningful calls in primates, because of a scarcity of comparative data, it is unclear to what extent analog forms might also exist outside of primates. Here, we address this ambiguity and provide evidence for rudimentary compositionality in the discrete vocal system of a social passerine, the pied babbler (Turdoides bicolor). Natural observations and predator presentations revealed that babblers produce acoustically distinct alert calls in response to close, low-urgency threats and recruitment calls when recruiting group members during locomotion. On encountering terrestrial predators, both vocalizations are combined into a “mobbing sequence,” potentially to recruit group members in a dangerous situation. To investigate whether babblers process the sequence in a compositional way, we conducted systematic experiments, playing back the individual calls in isolation as well as naturally occurring and artificial sequences. Babblers reacted most strongly to mobbing sequence playbacks, showing a greater attentiveness and a quicker approach to the loudspeaker, compared with individual calls or control sequences. We conclude that the sequence constitutes a compositional structure, communicating information on both the context and the requested action. Our work supports previous research suggesting combinatoriality as a viable mechanism to increase communicative output and indicates that the ability to combine and process meaningful vocal structures, a basic syntax, may be more widespread than previously thought.
 
 
Component, group and demographic Allee effects in a cooperatively breeding bird species, the Arabian babbler (Turdoides squamiceps). Oecologia
In population dynamics, inverse density dependence can be manifested by individual fitness traits (component Allee effects), and population-level traits (demographic Allee effects). Cooperatively breeding species are an excellent model for investigating the relative importance of Allee effects, because there is a disproportionately larger benefit to an individual of being part of a large group. As a consequence, larger groups have greater performance than small groups, known as the group Allee effect. Although small populations of cooperative breeders may be prone to all levels of Allee effects, empirical evidence for the existence of a demographic Allee effects is scarce. To determine the extent to which Allee effects are present in a cooperatively breeding species, we used a comprehensive 35-year life history database for cooperatively breeding Arabian babblers (Turdoides squamiceps). Firstly, we confirmed the existence of a component Allee effect by showing that breeding individuals in large groups receive greater benefits than those in small groups; second, we confirmed the existence of group Allee effect by showing that larger groups survive longer. And thirdly, we identified a demographic Allee effect by showing that per capita population growth rate is positively affected by population density. Finally, we found that emigration and immigration rates, although dependent on group size, do not buffer against component and group-level Allee effects becoming a demographic Allee effect. Our finding of the existence of all three levels of Allee effects in a cooperative breeder may have important implications for future research and conservation decisions.
 

This morning I awoke to a science media awash with reporting on a new paper produced from a field site that I spent many years at. The work is a new paper, published in Nature, on meerkats and competitive growth. To name (and link) just a few of the news stories, it was covered by the Guardian, Science, Science Daily and National Geographic – pretty widespread and prestigious, not to mention far reaching, media coverage. I don’t want to go into all the ins and outs of this new bit of research, as exciting as it is, as you can just click on the above links or read the article yourself (link and abstract at the end). But the gist is that in meerkat litters, if your siblings are growing faster than you then you increase your food intake and growth rate to try and match them, this was elucidated using some really great experiments (details of that later). This is really important for cooperatively breeding species like meerkats, where reproductive skew is high with only a few individuals ever reaching dominance. So in order to maximise their chances of competing with their litter mates, meerkat pups up their food intake. Simples!
 
What I want to briefly expand on here is the importance of long-term research in this discovery. The study animals used for this work are wild, they all live out their lives in the Kalahari and are beset by the hardships of competition, constant foraging and threats of predation. However, these meerkats (like the babblers that I worked on) are habituated to human observation. This habituation has huge benefits, it allows close observation of interactions, it allows for identifying individuals, it allows for field experiments to be done (be they playing back specific calls or tactically feeding specific meerkats as they did here!) but in the case of the meerkats (and the babblers) it allows researchers to weigh them multiple times a day. You may ask what does this have to do with long-term research? Well meerkats are naturally very skittish, they’re not very big and lots of things want to eat them. It typically takes between 12-24 months to habituate a group up to a good level, from spending hours sitting at a burrow as still as possible but humming the habituation song all the way to walking with them and weighing them. And to have a study population of between 16-25 groups that is a lot of man hours. To get around all of those groups on a regular enough basis you need a small army of researchers, constantly collecting weights, life-history data and helping out with experiments.

This work is also built upon decades worth of other research on these animals, which is not possible without uninterrupted observation. Slowly but surely this work unravelled the natural history of these animals, opening up interesting research questions, which in turn attract researchers with other interest that open up new avenues of research. Long-term studies thus offer a great avenue to expand our knowledge just simply by persisting in one place over a long time. They also tend to build up a network/family tree of researchers who have either worked or done PhDs or post-docs there, and once they move on they are a valuable link between research institutions. Ironically, even though the meerkats have been shown to not be very incestuous, the meerkat research are less averse to such behaviour!
 
All of these ideas are summed up in a great paper entitled: Individuals and populations: the role of long-term, individual-based studies of animals in ecology and evolutionary biology. Long-term study populations exist in many species across all taxa. The meerkats, red deer, Arabian babblers, blue tits, marmots, big horn sheep and pied babblers are just the ones that come off the top of my head. All of these have contributed massively to our understanding of behavioural ecology, population biology and conservation. So when I see a paper like this new meerkat paper I don’t just see the work of the named authors (shout out to Matt Bell – legend) but also to the tens to hundreds of volunteer researchers who have kept those projects going over the decades of their existence (of which I was once one). I hope that after reading this that you’ll appreciate that too.
  
Huchard et al. (2016) Competitive growth in a cooperative mammal. Nature, doi:10.1038/nature17986
 
In many animal societies where hierarchies govern access to reproduction, the social rank of individuals is related to their age and weight1, 2, 3, 4, 5 and slow-growing animals may lose their place in breeding queues to younger ‘challengers’ that grow faster5, 6. The threat of being displaced might be expected to favour the evolution of competitive growth strategies, where individuals increase their own rate of growth in response to increases in the growth of potential rivals. Although growth rates have been shown to vary in relation to changes in the social environment in several vertebrates including fish2, 3, 7 and mammals8, it is not yet known whether individuals increase their growth rates in response to increases in the growth of particular reproductive rivals. Here we show that, in wild Kalahari meerkats (Suricata suricatta), subordinates of both sexes respond to experimentally induced increases in the growth of same-sex rivals by raising their own growth rate and food intake. In addition, when individuals acquire dominant status, they show a secondary period of accelerated growth whose magnitude increases if the difference between their own weight and that of the heaviest subordinate of the same sex in their group is small. Our results show that individuals adjust their growth to the size of their closest competitor and raise the possibility that similar plastic responses to the risk of competition may occur in other social mammals, including domestic animals and primates.

In the spirit of many of my previous blogs I am going to write about a new paper written by someone I know. This may sound like some sort of nepotism, not that many people really read my blog, but this new paper has actually made quite a splash and so I’m really just following a great new science story. If you want to see some of the other coverage then click on these links: Science, Sci News, Science Daily, or PLoS Blogs. (The abstract and link to the paper in question is at the bottom of the blog)
 
This new piece of research is a product of the Hot Birds team at the Fitz in Cape Town, with Tanja van de Ven (lead author) spending many gruelling hours in the Kalahari heat with fairly complex equipment. The team, and Tanja’s, aim is to investigate how birds cope with rising temperatures using species that already exist in the hard thermal conditions of the Kalahari. One of their papers looked at the impact of heat stress on foraging in pied babblers. However, Tanja’s work focuses on yellow-billed hornbills, a species of bird that nests inside trees, with the female sealing herself into this cavity. This reproductive adaptation is great for protecting your eggs and female from predators but it can limit your ability to control your temperature, as you’re pretty stuck (it also means that the female and chicks are 100% dependent on the male for their nutritional needs – such a cool system for male-female and parent-offspring dynamics!!!).
 
The obvious feature of this bird, hopefully you have either clicked on the link or already know what a hornbill looks like from your bird knowledge or from childhood exposure to the Lion King, is that they have a massive long bill. The beak of a bird is not just lifeless tissue like finger nails but very much a living structure and as such has a profusion of blood vessels. Just like the thermoregulation that takes place in humans, where capillaries close to the surface are constricted or relaxed to either conserve or radiate heat, hornbills appear to have the same ability with the blood vessels in their beak. As the ambient air temperature increases more blood is pushed into the hornbill’s beak, allowing heat to be lost through radiative heat transfer. This is similar to toucans, as a recent study has found, but in the toucan this process accounts for upto 60% of non-evaporative heat loss compared to just 8% in the hornbill. There are a number of potential reasons for this: the toucans have much larger bills, hornbills have a harder bill (maybe an ecological adaptation to how they forage?) and toucans start dilating their blood vessels at lower temperatures.
 
This type of research is crucial for understanding how organisms are physiologically adapted to their environment. It enables researchers to better understand the environmental limits that a species may be able to cope with and allow predictions as to the impacts of climate change. It’s also pretty cool too.
 
 
van de Ven et al. (2016) Regulation of heat exchange across the hornbill beak: functional similarities with Toucans? PLoS One
 
Beaks are increasingly recognised as important contributors to avian thermoregulation. Several studies supporting Allen’s rule demonstrate how beak size is under strong selection related to latitude and/or air temperature (Ta). Moreover, active regulation of heat transfer from the beak has recently been demonstrated in a toucan (Ramphastos toco, Ramphastidae), with the large beak acting as an important contributor to heat dissipation. We hypothesised that hornbills (Bucerotidae) likewise use their large beaks for non-evaporative heat dissipation, and used thermal imaging to quantify heat exchange over a range of air temperatures in eighteen desert-living Southern Yellow-billed Hornbills (Tockus leucomelas). We found that hornbills dissipate heat via the beak at air temperatures between 30.7°C and 41.4°C. The difference between beak surface and environmental temperatures abruptly increased when air temperature was within ~10°C below body temperature, indicating active regulation of heat loss. Maximum observed heat loss via the beak was 19.9% of total non-evaporative heat loss across the body surface. Heat loss per unit surface area via the beak more than doubled at Ta > 30.7°C compared to Ta < 30.7°C and at its peak dissipated 25.1 W m-2. Maximum heat flux rate across the beak of toucans under comparable convective conditions was calculated to be as high as 61.4 W m-2. The threshold air temperature at which toucans vasodilated their beak was lower than that of the hornbills, and thus had a larger potential for heat loss at lower air temperatures. Respiratory cooling (panting) thresholds were also lower in toucans compared to hornbills. Both beak vasodilation and panting threshold temperatures are potentially explained by differences in acclimation to environmental conditions and in the efficiency of evaporative cooling under differing environmental conditions. We speculate that non-evaporative heat dissipation may be a particularly important mechanism for animals inhabiting humid regions, such as toucans, and less critical for animals residing in more arid conditions, such as Southern Yellow-billed Hornbills. Alternatively, differences in beak morphology and hardness enforced by different diets may affect the capacity of birds to use the beak for non-evaporative heat loss.

  There are many species that do not just exist with one specific colour pattern. These different colourations are called polymorphisms, existing in a variety of taxa from crabs to lizards to birds. There have been many explanations for the existence of these differences within a species, from protecting against predators to being important for mate choice. There is even a species of lizard, the side-blotched lizard, that exists in three colour morphs that are linked to their behaviour that was famously studied by Barry Sinervo. The orange males are more dominant, the blue males cooperate and the yellow males mimic females. These three morphs live in a state of perpetual flux as none can get the upper hand in the mating game. Basically colour morphs are interesting and we’ve really not touched the surface in understanding the evolutionary mechanisms that lead to and maintain them.

Some really cool studies have been done at the Percy FitzPatrick Institute in Cape Town by Arjun Amar to investigate the two colour morphs of the black sparrowhawk (Accipiter melanoleucus). These majestic birds are either a white or black morph. A new paper has just come out showing that one of the factors that may be keeping these morphs going is the difference in hunting success that they face. Black morphs, unsurprisingly because of their colour, have a higher success in low light levels, while their white breather have the opposite success rates. These success rates tie in with the breeding season of these morphs and may go a long way to explaining the variation in morph distribution across the species South African range. Abstract below:

Tate et al. (2016) Differential foraging success across a light level spectrum explains the maintenance and spatial structure of colour morphs in a polymorphic bird. Ecology Letters
Detectability of different colour morphs under varying light conditions has been proposed as an important driver in the maintenance of colour polymorphism via disruptive selection. To date, no studies have tested whether different morphs have selective advantages under differing light conditions. We tested this hypothesis in the black sparrowhawk, a polymorphic raptor exhibiting a discrete white and dark morph, and found that prey provisioning rates differ between the morphs depending on light condition. Dark morphs delivered more prey in lower light conditions, while white morphs provided more prey in brighter conditions. We found support for the role of breeding season light level in explaining the clinal pattern of variation in morph ratio across the species range throughout South Africa. Our results provide the first empirical evidence supporting the hypothesis that polymorphism in a species, and the spatial structuring of morphs across its distribution, may be driven by differential selective advantage via improved crypsis, under varying light conditions.

These results tie in nicely with previous work that has looked at the ratio of morphs across South Africa. This work found that the Cape peninsula had a very high proportion of black morphs but that this was unlikely to do with a founder effect. More likely it was because of higher rainfall rates during the breeding season, fitting nicely with the recent hunting findings. However, as is often the case in biological systems, hunting and light are not the only potential drivers for polymorphism in this species. It turns out that black morphs have a lower parasite load than white morphs.
 
The great thing about this particular subsection of research on the black sparrowhawk is that it all initially came from the observation that there seemed to be more black morphs in Cape Town than normal. This simple natural history note has spawned a growing number of scientific papers and led to wonderful new insights into evolution. So the next time you notice something when walking about just think that it might be far more interesting than may initially be apparent!

Other black sparrowhawk papers:
 
Amar et al. (2014) Clinal variation in the morph ratio of Black Sparrowhawks Accipiter melanoleucus in South Africa and its correlation with environmental variables. Ibis

Lei et al. (2013) Differential Haemoparasite Intensity between Black Sparrowhawk (Accipiter melanoleucus) Morphs Suggests an Adaptive Function for Polymorphism. PLoS ONE

On Sunday David Attenborough will turn 90. He is possibly the person who has done most to advance the public love for the natural world and in his long career has inspired generations to study the wonderful array of biodiversity we have on this blue-green dot. His tireless, and peerless (sorry but no one else really comes close to him) work has kept nature in the minds of millions and hopefully helped to highlight our impact on the natural world.

His simple blue shirt and chino combo has graced our screen for decades. The melodic tones of his voice and childlike wonder and excitement have relayed the wonders of nature and narrated the epic life stories of untold numbers of species. From plants to insects, mammals to birds, Polar Regions to deserts, and ocean floors to darkest caves, he has helped to illuminate the natural world (IMDb of Big Dave). The most amazing thing is that he seems to be working almost as hard now as he ever has, even abseiling down the new Cambridge Conservation Campus to open it!
Everyone will have differing memories of this towering figure of natural history. Below I tell mine. But here are a few of his “best bits”: LINK

I have been lucky enough to hear the great man speak. He had been at university with the son of Cecily Niven, the woman whose hard work saw the setting up of the Percy FitzPatrick Institute of African Ornithology. They had been good friends and Sir David had agreed many years ago to come and speak at the university. However, over the years of their friendship he had never been able to make it to the Cape to fulfil his promise. He had now made the journey to honour the request made to his now departed university chum. His topic was Birds of Paradise, a subject close to his heart as can be evidenced in his documentary retracing the steps of Wallace to Papua New Guinea. This specious and vibrant group of birds have fascinated naturalist and behaviour biologists for years, with their amazing plumage and courtship displays. His speech was a mesmeric blend of footage, photos and wonderful anecdotes that was topped with a generous sprinkling of natural history. At the end the floor was opened to question, which was a big job as the Baxter Theatre was at full capacity and the crowd were eager to ask questions from a lifetime of viewing the great man on screen. The top question came as a women stood up, unzipped the back of her dress and turned to reveal a full back tattoo of a bird of paradise. She asked ‘what is your favourite species of bird of paradise?’ to which Attenborough replied with a wry smile ‘it would be ungallant of me to say any other then the one on your back.’

I was also fortunate to be able to ask him a question. I had recently seen one of his documentaries where he explained trilobites and the amazing fossils to be found in Morocco. I nervously got up, in front of not just the other PhD students but also most of the Biological Sciences faculty (who had come along even though they weren’t supposed to) and I asked him what his favourite trilobite was. Without really pausing to start his answer and a twinkle in his eye he began to speak, and I was initially saddened. He seemed to either not have heard the question or misunderstood it. My hero, in his dotage was afflicted by senility. However, I couldn’t have been more wrong. With a story telling panache and with witty repartee he spun a long story that went on for almost 10 minutes and culminated in a perfect answer to my question. He was still razor sharp. Afterwards I rushed back to the department with a friend, as we’d heard he was back at the Fitz, and I got a picture with my idol!  

Here is a wonderful Youtube link to 16 of David Attenborough's best moments: LINK

I hope that he can go on for many more year, but I realise that 90 is already a great innings. This man is truly one of the greatest modern Britons, whose work exemplifies what the BBC stands for: public service broadcasting. He has pioneered and championed the best natural history film making and in so doing so done a great service to the natural world, which he is so endlessly fascinated by.

He is my hero.

Last week the Kenyan government burnt a huge stock of Ivory. Here's a link to footage of the multiple tusk bonfires: LINK

This is an impressive act but the question still remains as the the best course of action that governments should take with their siezed Ivory. Ivory is a commodity like anything else: sugar, coffee or chocolate. Supply and demand economics impact on its price. Will destroying a large amount of Ivory drive up price? This could have the knock on effect of increasing poaching as the rewards are greater. Alternatively, such a publicised display may drive down demand and so reduce poaching levels. The poaching networks are complex, crossing continents and with multiple levels and middlemen. Thus, it may be impossible to know the direct impact of Kenya's decision.

There are alternative paths that other Aftican governments have chosen. Under the supervision of CITES, four southern African countries (Botswana, Namibia, South Africa and Zimbabwe) carried out auctions to accredited buyers and raised $15.4 million for conservation. Most of this Ivory was legal Ivory, collected from elephants that had died naturally in national parks. I know private game reserves do the same, and a reserve close to my PhD field site flew about $4 million worth of rhino horn to a safe location. But is this type of sale right? Doesn't it just maintain a market for poached Ivory? Or does it allow governments to generate revenue to protect enigmatic species (and probably loads of others in the process)? (https://cites.org/eng/news/pr/2008/081107_ivory.shtml)

This is the forefront of modern conservation. It's where conservation science, economics (macro and behavioural) and human geography collide. This is one reason for the building of the new Cambridge Conservation Campus, recently opened by Sir David Attenborough. These questions are not easy to solve but they are solvable! http://www.conservation.cam.ac.uk/cambridge-conservation-campus