More generally, the topic should be broad enough to allow every person to look for anecdotes (did you know there was once a ‘scavenging bat called *Necromantis*?’ and to bring these together in an interesting, more generalised framework. Continue reading “A recipe for collaboration”
I have recently returned from a field trip to Swazliand where I was working with my long-time collaborator Prof Ara Monadjem to tag two African White-backed Vultures with high-spec trackers. These devices were purchased with a $20,000 grant from the Critical Ecosystem Partnership Fund and are currently sending their locations every minute via the mobile phone network. Up to now we have no idea where the Swazi population of this species forages and this is something the tracking data will reveal. With only a few weeks of tracking data we can see the birds have already ventured into Mozambique and South Africa.
It’s coming up to winter so people will be conscious that our garden birds need a helping hand to get through the cold months. Bird feeders will be stocked, bread served up and water dished out. In the UK alone, almost half of households provide supplementary food for birds throughout the year. And although songbirds are usually the species that come to mind when we think of provisioning food the same principle can apply to more exotic birds, notably vultures. Indeed conservationists have supplied extra food to these scavengers for decades. Instead of bread or berries, a carcass is left out for the vultures to feed on. A recent paper of ours advocates this technique for a population of African White-backed Vultures in Swaziland.
This country is home to the densest breeding population of this species so we should do our best to conserve them given the huge declines suffered by vultures throughout the Old World. In the paper we showed times when there isn’t enough food in Swaziland to feed the whole population which means the birds are forced to forage farther afield, most likely in South Africa. On the face of it this doesn’t seem problematic because South Africa has huge populations of herbivores which could supply carcasses to vultures. But the birds must fly over unprotected areas as well. This increases their chances that they’ll encounter a poisoned carcass, perhaps set out by a farmer to kill the terrestrial carnivores harassing his livestock.
It’s well known that vultures are particularly sensitive to poisons, especially NSAIDs. Their group foraging behaviour makes them even more susceptible too, the discovery of a carcass by one individual will bring in the rest of the soaring birds in visual range. The hope with creating vulture restaurants is the birds will focus on foraging for carrion in Swaziland, minimising the risk of poisoning.
Yet there are well known problems with supplying supplementary food for animals in general. They may act as an ecological trap for instance, drawing the birds into an area only for the fickle humans to stop the supply of food. Carrion is an unpredictable resource so vultures forage in a characteristic way to improve their chance of encountering it. If food is supplied in a predicable way there is a fear we may disrupt these behaviours. Another recently realised danger in providing supplementary food is that it can attract unwanted guests. Sites tailor made for vultures in South Africa were shown to draw in jackals and hyenas.
Given these issues practitioners need to think carefully about how they provide food. Perhaps the best approach is a series of sites supplying food at random which would best represent the distribution of naturally occurring carrion.
Conservationists try their best to stop endangered species sliding to extinction and keep the habitats of these life forms intact. Captive breeding programs, national parks, management of invasives etc. are all common measures in conservancy. But how do we know that these methods work? Perhaps an invasive species is actually serving as a food source for the conservation target, and, by killing off the former, we imperil the latter further still. Fortunately, we can avoid such disasters through experimentation and modeling, in other words, with some good science.
Consider the case of the Cape Vulture (Gyps coprotheres) in Southern Africa. This large scavenger patrols its habitat, often a huge range, foraging for carrion. It’s suffering a decline in numbers for a variety of reasons. Carcasses are often poisoned to kill predators that take farmer’s livestock with the vulture an innocent victim. Their social nature means tens of the birds can be killed by a single toxic carcass. More direct persecution comes in the form of poachers who have taken to poisoning the carcasses of their quarry. The rationale is to wipe out vultures who will identify the location of future crimes. Then there are accidental deaths that arise from bird collisions with electricity pylons and wind turbines. And it will take some time to convince otherwise those who value vulture brains for their clairvoyant properties.
Fortunately, some vultures survive these incidents and that’s where rehabilitation centres come in. People at these facilities nurse the birds back to health and release them into the wild. The problem is some of the injuries suffered may be insidious, leaving a permanent but unnoticeable effect on the animal’s health.
We used resightings data on a population comprised of rehabilitated and wild birds to estimate their chances of survival and found that the rehabs have a significantly lower chance of surviving year on year (90% Vs 72%). By modeling different proportions of rehab and wild birds we showed that a 50:50 mix of the two groups is the threshold beyond which the population will decline.
That’s not to say that we think rehabilitation is a bad idea, it’s obviously better to get the bird back in the wild where it can contribute to the survival of the species than leave it to die from its injuries. Rather we suggest that vulture conservation should be focused on prevention instead. This is achievable. In India, farmers have stopped using drugs on their cattle which poisoned the vulture population en masse. Pylons and turbines can be equipped with signals that alert the birds to their presence.
Conservation practice coupled with a scientific understanding can only better our ability to stop the slide to extinction.
Last month I spent a month in Mbuluzi Game Reserve in Swaziland attempting to build a walk-in trap that will allow me to capture vultures. I want to be able to tag the birds with GPS trackers and ask a host of interesting questions from which a flood of Nature papers will follow.
We’ll have to wait for the vultures to get habituated to the area before adding the front to the trap. Once this happens we can proceed. So this is a ‘to be continued’…
My PhD involves studying the foraging behaviour of vultures. So far I’ve done theoretical work and also had the luck to get some second hand empirical data. But I’d like to be able to get some field data first hand. To that end I’m setting off to Swaziland on Saturday with the intention of building a vulture restaurant and a walk-in trap. The first item takes a little explaining. Vultures are carrion feeders, which means their food source is unpredictable, the bird never knows when the next wildebeest is going to drop dead. So they’re quite sensitive to declines in food availability. But a vulture restaurant is a conservation tool that acts as a supplementary feeding station for the birds. The people organizing the restaurant can deposit carrion at the site thereby providing an extra food supply for the vultures. This is done to keep the birds within an area, to feed them during times of food scarcity or in my case to aid in their capture.
Alongside the restaurant we’re going to build a walk-in trap, a simple structure that the birds walk into before we close the door behind them and have a PhD’s worth of data points. Well, it’s not quite that easy. I want to be able to find out to where these birds are foraging at a high temporal resolution so we will be putting GPS tags on the vultures once we capture them. This means some poor soul will be entering the trap and extracting the birds one by one, each animal getting tagged before being released back into the wild. I should stress this has been done before on many occasions and the birds are all freed within minutes without any ill effects.
So far a lot of research done in this area provides us with broad-scale movement patterns. With my finer scale data I’ll hopefully be able to pick out some quite specific aspects of vulture foraging behaviour. Wish me luck!
On the 15th and 16th April we had one of my favourite events at Trinity College Dublin: the annual School of Natural Sciences Postgraduate Symposium. Over the course of two days many of our PhD students presented their work to the School. We also had two amazing plenary talks from Dr Nick Isaac (CEH) and Professor Jennifer McElwain (UCD). For those of you who are interested in exactly what we work on here at EcoEvo@TCD, here are the abstracts from the PhD student presentations. Check out the TCD website for more details!
Rebecca Rolfe [@rolfera]: Identification of mechanosensitive genes during skeletal development: alteration of genes associated with cell signalling pathways.
Mechanical stimulation is important for correct formation of the skeleton. Mutant mouse embryos that develop with no skeletal muscle have altered mechanical stimulation resulting in specific defects in ossification and joint formation. We tested the hypothesis that mechanical stimuli influence the regulation of genes important in skeletal development by analysing the transcriptome of muscle-less and control skeletal tissue. We found 1,132 independent genes are differentially expressed with significant enrichment of genes associated with development and differentiation and cytoskeletal architecture. In particular, multiple components of the Wnt signalling pathway are affected. Further analysis will examine the mechanisms by which mechanical stimulation influences gene expression and differentiation, findings that are relevant to controlling differentiation in stem cell based regenerative therapies.
Adam Kane [@P1zPalu]: Scrounging Scavengers: Vultures acquire information on carcass location from scavenging eagles.
Vultures have an ecological role as obligate scavengers. In addition to being unable to kill prey for themselves we suggest that they are dependent on other species to locate food. Our analyses of bird arrival times at carcasses show that vultures join a carcass after discovery by raptors more often than expected by chance. We develop a game-theoretic model showing that such an interspecific producer-scrounger game is evolutionary stable when vultures are dominant to raptors in agonistic interactions over food. This hierarchy was confirmed at the carcass. Vulture populations are declining so our findings have implications for the conservation of the group.
Sarah Hearne [@SarahVHearne]: Intrinsic and extrinsic factors shape global marine diversity.
Intensifying anthropogenic pressures on ecosystems on a global scale have lead to an increased focus on the relationships between biodiversity and stability. Many studies of biodiversity have focussed on changes in diversity measures over relatively short timescales. However, there are also long-term changes in biodiversity which have been revealed through the fossil record. My project is examining global marine invertebrate diversity throughout the Phanerozoic Period (540my to present) to determine the causes of the cycles of extinction and origination over this time period. Using a new technique, convergent cross mapping, it has been shown that extinction and origination are both driven by diversity and each other, while extinction is also causally affected by temperature and origination by sea level.
Aoife O’Rourke: Spring foraging resources and the behaviour of pollinating insects IN grey dune ecosystems.
Grey dunes are a priority habitat under the EU Habitat Directive. They often contain creeping willow (Salix repens L., Salicaceae), which is suggested to be an important early season resource for bees and other obligate flower visitors. However, there is a paucity of empirical evidence to support this claim. We examine the springtime activity of obligate flower visitors in the grey dune ecosystem in relation to nectar sugar concentration and composition, relative abundance (%) of essential amino acids in pollen, and the abundance of floral units of S. repens and co-flowering plants in the environment. We also investigate the effect of S. repens presence on the abundance and species richness of solitary bees, bumblebees and hoverflies. Insect focal observation, pan-trapping and chemical analyses techniques were used to explore our research questions. Results will be presented and discussed in the context of managing habitat to increase resource availability for pollinators during spring.
Deirdre McClean [@deirdremcclean1]: The world in a bottle: Investigating stability and social transactions in microbial communities. *Best talk 1/2*
Understanding how perturbations affect the long term stability and dynamics of different systems has been a core challenge for ecological research. Identifying the mechanisms by which communities respond to and recover from different perturbations is of vital importance for assessing the impacts of anthropogenic pressures on the environment. Long term, multi-generational field studies are typically impractical, costly and confounded by a host of other ecological variables that need to be accounted for. Logistically feasible model systems are therefore needed in order to test more generalized ecological and evolutionary theory. Here we use experimental microcosms to examine the interactions among food web structure, habitat modification and social interactions in order to determine how these might moderate the effects of perturbations on stability.
Brian McGuinness: Escallonia spp. fungal pathogens.Sadly Brian missed the symposium but we still have his abstract…
A fungal disease affecting plants from the genus Escallonia has become a significant problem for both the nursery industry and for gardeners who use it as an ornamental boundary hedging. Development of lesions generally starts on older leaves throughout the plant usually causing some degree of defoliation ranging from mild to severe and sometimes resulting in plant death. We show how susceptibility of Escallonia to leaf spot disease varies across species and infra-specific taxa by in-situ assessment. No 100% genetic match currently exists for the organism causing the leaf spotting which is the same organism affecting plants in the U.K. Next steps include generating a full taxonomic description based on morphology and conducting next generation sequencing to identify any population differences that may exist.