ecology Archives - Page 7 of 10

15/04/2013

Disney Ecology

In light of the current stresses of exam season, I have been contemplating my parallel educational history. Of equal, if not superior, importance to any stage of my conventional academic life, I have had a Disney education. If I visit medieval castles or forts rich in feudal history I can’t help but mentally locate Rapunzel’s tower and contemplate the prince’s access route. My Greek mythological references are entirely based upon Disney’s Hercules and any mention of Rudyard Kipling is incomplete without at least one verse of the Bare Necessities. Zoological education is no exception. Early Disney films were rather loosely based on real zoological principles – I don’t remember Snow White using any Pavlovian theory to behaviourally condition her furry friends to help with the housework. Similarly, Mary Poppins serenaded an American robin from her London home because studio executives thought the sight of a European robin would be too confusing for their target audience. However, some recent Disney tomes are more grounded in realistic ecology. Disney was my first introduction to fundamental ecological and behavioural concepts as varied as breeding coalitions, mutualistic relationships and inter-specific communication.

Responsible for introducing Swahili phrases to a generation of Timon and Pumbaa fans, the Lion King is a Disney classic, both as a film and more recently as a highly popular stage musical (which is coming to Dublin soon – even if you don’t normally like musicals you must go to this show for the most incredible stagecraft you will ever see). The film marked one of the first times that animators made a specific effort to study their animal subjects to make their movements and behaviours as realistic as possible. Prior to the release of this film, my four-year old self didn’t know that male lions, often brothers, form coalitions to take over prides or that female lions take a cooperative, crèche approach to raising their offspring. Cooperative behaviour in lions continues to spark interest and research to understand why lions are unique among big cats in exhibiting these social tendencies. Of course, some creative licence remained in Disney’s depiction of their feline heroes – the voice of Darth Vader is sadly absent from the Serengeti and male lions don’t lead a troupe of goose-stepping hyenas in a song of revolution. Similarly, rather than a “king and queen”, there’s an equal dominance status within male members of a coalition and within adult females in a pride (unfortunately socially equal characters don’t lend themselves easily to a re-telling of Hamlet). Despite the sprinkle of Disney magic however, the basic ecological premise of Simba’s pride remains grounded in fact.

My ecological horizons were further expanded by Finding Nemo’s depiction of the mutualistic relationship between clownfish and the anemones they call home. It’s a deceptively simple relationship – the anemone’s sting provides the fish with a predator-free habitat while Nemo and his friends help keep the anemone free from parasites. However, many of the finer details underlying this interaction continue to spark research interest (and I’m obviously not the only one to have experienced a parallel Disney education). Nemo has provided evidence that mutualistic interactions tend towards a nested structure. More recently, the way clownfish move their fins has been identified as helping to increase anemones’ oxygen consumption at night – although, hampered by a malformed fin, I wonder whether Nemo’s personal anemone is gasping for breath a bit more than the other anemones? Furthermore, Finding Nemo did not neglect my geographical education – I now know that to get from the Great Barrier Reef to Sydney it’s just a short ride on the East Australia Current – and if I meet a turtle on the way, just call him “Dude”, Mr Dude is his father.

Thanks to Disney, Nemo’s pal Dory is another star of every aquarium. Forgetful but lovable, Dory was my first introduction to the realms of interspecific communication. While Dory speaks whale, it appears that some whales can learn to talk back. A captive beluga whale in San Diego seems to modify its call to mimic human speech. Neither of these examples are true interspecific communication; Dory’s valiant efforts to converse were unsuccessful and the Californian beluga’s “human” vocalisations appear to be relicts of an ability to mimic other whale species. In both cases, information is not passing between fish and whale or whale and human. Though who knows, perhaps Finding Nemo 3 will be a story of the quest to discover the Rosetta Stone for interpreting whale speech…

So through the talking animals, improbable alliances (why a meerkat and warthog??) and heart-warming moral tales, look out for the ecology in your next Disney film. Combining their subliminal ecological messages with the excellent work of the Disney conservation fund hopefully many more generations will experience a Disney ecological education.

Author

Sive Finlay: sfinlay[at]tcd.ie

Photo credit

wikimedia commons

27/03/201327/03/2013

Tyre Pressure

I’ve recently been spending a lot of time working with undergraduate students and marking their work and much of it has been on the subject of evolution and natural selection. This can be a difficult topic to clarify in the mind of younger students and it’s often difficult to recall specific examples which can be easily explained. Usually you have to come up with some hypothetical situation whereby some selection pressure drives a population towards evolutionary change. A newly published study in Current Biology by Brown and Brown however provides a beautiful (and more importantly brief) example of evolution and natural selection at work.

They have been studying populations of cliff swallows (Petrochelidon pyrrhonota) in Nebraska for almost thirty years, attempting to evaluate the costs and benefits of group living in these highly social birds. In an interview with John Dankosky lead author Charles brown explains how his habit of checking road killed birds for rings (or bands, as they are called in the US) led to an intriguing discovery. Firstly they noticed that over the years fewer and fewer birds were being killed on the roads (Figure 1), but also that these road killed birds tended to have longer wing lengths compared to individuals of the general population.

Figure 1. Change in wing length and number of road killed swallows (From Brown and Brown 2013).

So if you are a cliff swallow why does having a longer wing make you more likely to be run over by a car? Well it all comes down to the angle of escape. Birds with shorter more rounded wings are able to take off more vertically compared to individuals with longer more pointed wings, essentially shorter winged birds can get out of the way of oncoming traffic more quickly. It seems that this selection pressure from vehicles has been driving (I make no apology for the pun) the evolution of shorter wings in this population of cliff swallows.

Cliff swallows are migratory birds, travelling from South to North America annually and longer more pointed wings are generally seen as an advantage when it comes to long distance flight. Therefore it seems that the shorter winged individuals may pay an energetic cost compared to their longer winged conspecifics, but this cost may be outweighed by the benefit of being able to avoid traffic. Whatever the case may be I think this study provides a nice example of selection pressures steering morphological adaptations along the road to survival. Next time a student needs clarification on this I’ll remember, tyre pressure.

Author

Keith McMahon: mcmahok[at]tcd.ie

Photo credit

Tommie Kelly (www.tommiekelly.com)

25/03/201325/03/2013

Bees and biofuels….what’s the buzz?

As oil prices sore and the future of world energy is uncertain, there is rising demand for alternatives to fossil fuels. From solar energy to wind to algae fuel and biodigestion, the alternatives are numerous. One alternative that has received substantial media attention is the use of bioenergy which involves the production of energy from crops including maize, sugarcane, elephant grass and oilseed rape which are grown specifically for energy purposes.

However, the debate over bioenergy crops is often heated. Do they compete with food crops and therefore increase prices in an already stretched market? Do bioenergy crops result in the destruction of tropical rainforest to clear new areas for farmland? And are bioenergy crops even carbon neutral to begin with?

One debate that has been investigated by researchers in Trinity as part of the Simbiosys project is whether bioenergy crops can have impacts on biodiversity – the animals and plants that live on and in farmland. Not only are these animals and plants an important part of our heritage, but they are the pollinators of our food crops, the insects that control agricultural pests and the organisms that help provide us with clean water and air. With two-thirds of Irelands land area used for farming, any changes in farming practice are likely to have knock-on impacts on biodiversity.

A study recently published in the Journal of Applied Ecology investigated how growing bioenergy crops impacts the bees and other pollinating insects that pollinate wild flowers, apples, berries, oilseed rape, clover and many other crops here in Ireland (in fact pollinators are required for approximately 1/3 of all the food we eat). It was found that although different types of insect responded differently, there were no decreases of pollinators in bioenergy crop fields in comparison to their conventional farming alternative. And for some pollinator groups such as the small solitary bees, the introduction of small amounts of different crops into agricultural areas may actually be beneficial.

However, bioenergy crops did not provide the stable nesting conditions needed for pollinators; almost all bumblebees chose to nest in the field margins and hedgerows surrounding the fields. Field margins and hedgerows also provided habitat for large numbers of other insects. The study concluded that small amounts of bioenergy production on existing farmland may provide a diversity of habitats for pollinating insects, but that changes in levels of production in the future may have different effects. Hedgerows and field margins should also be maintained during bioenergy production as they are important nesting and forage sites for pollinating insects.

Although bioenergy crops in their current form seem like good news for bees, the future may be less certain. Growing these crops over larger areas rather than in individual fields, or the replacement of forests or meadows rather than existing arable (tilled) land, may have very different effects. With EU targets of 20% energy from renewable sources by 2020, and bioenergy incentives for farmers, we can expect further changes in this developing sector over the next few years.

Author

stanleyd[at]@tcd.ie

Photo credit

Dara Stanley

13/03/2013

Geese vs. Cyclists

From October onwards, when most of our resident wildlife is battening down the hatches to endure the impending bleak winter months, flocks of Brent Geese are very welcome visitors to Ireland. Their arduous journey to our shores is impressive for both its distance (approximately 3,000km from Arctic Canada) and the route taken: long-distance sea voyages punctuated by stop-overs in Greenland and Iceland before they reach Ireland. The necessity to escape harsh Arctic winters is very understandable. What’s not clear is why Brent geese undertake Atlantic crossings instead of following other geese species that journey south across the American continent. Whatever twist of evolutionary fate is responsible, there’s no doubt that we are lucky to receive annual visits from such intrepid voyagers.

I’m sure many Dublin residents would agree that sharing seaside walks with companiable small family groups of geese or witnessing one of the chattering fly-overs of a large flock undoubtedly brighten up an otherwise bleak winter’s day. However, a recent Irish Times article identified Brent Geese as the enemies of an unlikely foe; urban cyclists.

For more than 10 years, the S2S group has campaigned to create a continuous cycleway for 22km around Dublin Bay, running from Sandycove on the south side to Sutton on the north side which, if completed, would be Europe’s longest seafront promenade and urban cycle-path. The plan would be a great amenity for both recreational and commuter cyclists – you only have to travel along the coast road from Fairview to Howth to witness the popularity of the existing cycle path along the black banks. Just 8 km of the route remain to be completed, mostly on the south side and a single 4km stretch from Sandymount to Blackrock is particularly controversial.

The proposed route would cut through EU protected bird habitats and, in particular, affect an area of eel grass consumed by Brent Geese. The National Parks and Wildlife Service (NPWS) is also concerned about the impact of the cycle way on other bird species which reside in protected areas in Booterstown.

While I’m often wary of articles alluding to stereotypical views of “conservation hippies” thwarting sensible developments, in this case I have to agree with councillor Barry Ward that there must be a solution which “inconveniences rather than displaces” the geese. No development affecting protected habitats should be undertaken lightly. In particular, since the majority of Brent geese overwinter at just 10 sites, Birdwatch Ireland lists their conservation status as “medium concern”. However, with their current population seemingly in good health and the plethora of suitable habitat which Dublin Bay has to offer, it seems unlikely that an 8 metre wide seafront path would have a major impact on the goose population.

I’m well aware that if every development took the attitude of “there’s plenty of habitat elsewhere” then there would be no protected areas left. In addition, I must admit my vested interest in seeing the cyclepath completed – I’m a recreational (i.e. fair weather!) cyclist and live in Sutton so the availability of 22km of off-road cycling on my doorstep is a very attractive prospect. However, if you observe the behaviour of geese along the existing cycleway they seem to be remarkably unperturbed by adjacent human activity and continue to forage just below the boundary wall. Surely the same coexistent relationship between cyclists and geese could be forged south of the Liffey?

Despite including the S2S cycleway as part of their development plan councillor Barry Ward argues that management of the Dún Laoghaire Rathdown county council seems to be reluctant to develop the cycleway. Beyond the legitimate concern that the proposed cycleway would pass through a protected area, there seems to be no specific predictions or estimations that the development would have an adverse effect on the geese. Rather than an issue of cyclist vs. geese, perhaps this story is really a case of scape geese taking the blame for a council’s reluctance or inability to fund and implement a new development?

Author

Sive Finlay sfinlay[at]tcd.ie

Photo credit

wikimedia commons

08/03/2013

Fly Away Home

The University of Exeter team visited Ireland this week as part of their ongoing investigation into the biology of the Brent Goose. This species has a remarkable migration, spanning from Northern Canada to Western Europe. The team collects DNA samples, blood for stable isotope analysis and various morphometric and behavioural data. We joined them on Wednesday to help out.

Author

Adam Kane: kanead[at]tcd.ie

Photo credit

Adam Kane

06/03/201306/03/2013

Brown Bears and Shit Science

In my on-going attempt to improve myself I recently attended a lecture by Paul Eric Aspholm on brown bear tracking. This was a much more enjoyable and informative lecture than the last one attended and full of such interesting facts that I just had to share them!

Though the brown bear (Ursos arctos) is found throughout Eurasia and North America the talk focussed on those living in Scandinavia (Norway, Sweden, Finland) and Russia west of the Ural Mountains. In the first half of the 19^th century Scandinavia implemented a cull with the intention of wiping bears out. This cull was halted in the 1930s and since then populations have rebounded. Much of the work by Mr Aspholm involved tracking bears to determine population size and movements across the region.

The focus of the talk was shit. Lots and lots of shit. Spring shit, which is mostly grass. Summer shit, which is mostly meat and bones (growing bears need calcium!) and autumn shit, which is mostly berries. The bears are so dextrous that they can pick and eat individual berries and can get through tens of kilos of blueberries in a day! Female bears are quite careful about where they defecate but the males are much more casual in their toilet habits, to the extent that they sometimes accidently walk in a previous bear’s deposit!

The shit is gathered by helpful hunters (who sometimes collect human shit by accident!) and is sequenced to obtain genetic information about the depositor which can be used to track individual bears. Other tracking methods involve collecting hair in hair traps (a line of barbed wire set in a square with a delicious – to bears – smelling lure in the middle) and collecting footprints in snow. This last method was the most innovative (to me, at least). Bears walking over snow will leave skin cells in their footprints. All the scientists have to do is collect a few footprints (around 5-7), melt the snow, get the cells and then sequence the DNA to get a complete genetic profile.

These methods enable researchers to track the habits of individual bears over many years and sometimes several countries. They have been able to show that the bear populations have rebounded well since the end of the cull, with around 8 females reproducing each year in Norway. The hope is to get that to around 15 females a year, still significantly lower than the estimated pre-cull population but a healthy size considering the amount of habitat currently available to them. Most surprisingly of all, the populations show no evidence of genetic bottlenecking or reduced even genetic diversity despite little movement between populations.

As a public service we were given some tips in case we ever come across a brown bear. The traditional advice is to sing. This is, surprisingly, true as it is a sound that only humans can really make. If you scream, you sound like a frightened animal and a perfect chance for a snack. If you shout, you sound like an aggressive animal looking for a fight and the bear is likely to oblige. We were advised not look into their eyes, and most importantly of all – don’t turn your back on it. This is apparently an invitation to play and bears play rough!!

It was an absolutely fascinating talk and I learned so much. Many thanks to Mr Aspholm for such an interesting lecture.

Author

Sarah Hearne: hearnes[at]tcd.ie

Photo credit

wikimedia commons

04/03/2013

Could the ‘drone’ be a new technology to survey African wildlife?

Nazinga Game Ranch is a protected area in southern Burkina Faso, dominated by clear shrub and woody savannah and home to one of the most important elephant populations of the Western Africa.

Researchers from the University of Gembloux Agrobiotech in Belgium tested one of the first unmanned aerial surveys to study the wildlife of Nazinga. They achieved this study using ‘drone’ technology i.e. a small Unmanned Aircraft System (UAS) (pictured). This technology was shown to have the potential to be a valuable alternative to current walk and light aircraft survey techniques.

The Belgian researchers tested different aspects of this new technology on the wildlife and more particularly on elephants. Firstly they wanted to know if the animals reacted when the UAS passed over and found no animal flight or warning reactions were recorded when the plane passed over at a height of 100 meters. Secondly they flew the UAS at different heights (from 100 meters to 700 meters) and showed that only elephants are visible at these heights (while the medium and small sized mammals are not). The pictures taken at a height of 100 meters do however allow easy observation of the elephants.

In the light of this information one elephant survey has been completed in Nazinga Game Ranch so far. This UAS aerial survey has revealed several advantages in comparison to the traditional plane based surveying: (1) an easier flight implementation as a very short airfield is needed, (2) low safety risks as there is no pilot on board, (3) higher reliability in rough weather conditions, and (4) a lower global cost. However, to be able to cover hundred kilometres at a time it is important to improve the flight time of the small UAS as for the moment it is quite low.

Technological improvement of some aspects of the drone will make it more efficient and in the future could compete the light aircraft to monitor the wildlife in Africa.

Author

Florence Hecq: fhecq[at]tcd.ie

Photo Credit

Vermeulen C, Lejeune P, Lisein J, Sawadogo P, Bouché P (2013) Unmanned Aerial Survey of Elephants. PLoS ONE 8(2): e54700. doi:10.1371/journal.pone.0054700

01/03/201301/03/2013

Fantastic Mr Fox

At the launch of our recent college Green Week, Trinity College presented the final stages of its bid to secure the Green Flag Award. Part of the assessment comprised a summary of the plants and animals which, along with the rarefied species of Drama studientis and the Lesser Spotted Theoretical Physicist, contribute to campus biodiversity. Foxes were included in this list which surprised me since I had never come across one campus.

Happily though, last Friday evening one made an appearance just in time for the end of Green Week. Displaying the characteristic “boldness” of its habituation to city life and unperturbed by the passing cars, bikes, and rugby players, a large, healthy-looking fox trotted along the road beside me and into a small patch of scrubby bushes outside the Physics building. It must be a member of the den that resides in the Provost’s Garden – which received celebrity status in a recent Irish Times article. It’s intriguing to speculate whether the Trinity foxes cavort on the cricket pitch long after the last reveller has left the Pav on a Friday night? Similarly, I would love to know whether they are exclusive Trinity residents or do they dodge the shoppers on Grafton Street to visit their cousins in St. Stephen’s Green? Perhaps they also visit Merrion Square – pausing along the way to pay homage to some long lost relatives entombed inside display cases within the Natural History Museum.

Urban foxes have received some bad press recently after the rather gruesome story of the fox which bit off a baby’s finger in south east London. The RSPCA was quick to stress that, while truly horrific, this incident was extremely unusual. Despite their reputation for pilfering unguarded bins, foxes are usually quite shy and wary of coming too close to humans. However, in the wake of the London attack, Mayor Boris Johnson, labelled urban foxes as a “pest and a menace” and there were many calls for a large-scale culling operation to be instigated.

These emotive responses to an isolated incident should not be allowed to dictate future policy for dealing with urban foxes. In his recent New Scientist article, Stephen Harris points out that we are more likely to be attacked by pet dogs rather than foxes and culling programs simply don’t work since new animals just move in to fill vacated areas. In his view, it’s human rather than fox behaviours which give cause for concern. He argues that natural history programs which show cavalier presenters coming in to close contact with wild animals encourage people to seek unnatural and sometimes dangerous proximity with urban wildlife. For example, leaving food out in the garden to attract foxes can lead to some great sightings of these beautiful mammals but placing that food close to a house or near open windows or doors is just asking for trouble. Moreover, feeding foxes is a divisive issue in itself – is it akin to leaving food out for birds or does it equate to just attracting unwanted pests into our gardens? Personally, I have no issue with leaving out scraps but buying cat or dog food just for foxes seems excessive, especially when our untidy cities are veritable all you can eat buffets for these city slickers.

Whether you regard them as pest or surrogate pet, foe or friend, foxes are an inescapable feature of urban landscapes. With Trinity’s campus as their playground, who knows what the one I saw gets up to after dark?

Author

Sive Finlay: sfinlay[at]tcd.ie

Photo credit

wikimedia commons

22/02/201318/02/2019

The buzz on neonicotinoids

On the 31st January, stimulated by a European Food Safety Authority report, the EU proposed banning three neonicotinoid insecticides which have been implicated in causing honeybee decline. These insecticides are widely-used, systemic (i.e. soluble enough in water to move around the plant’s vascular system to nearly all plant tissues), and, like nicotine, affect the insects’ central nervous system. They are highly effective at reducing insect pests that feed on crops and reduce yields and value, and many farmers are concerned about the effect the proposed ban will have on crop production. But these insecticides can also end up in the nectar and pollen of crops (as well as in the soil and in non-crop plants), and thus can have unintended side-effects on beneficial, nectar-feeding insects, who act as pollinators. Especially bees.

Bee decline has become a hot topic with scientists, the media, the public and even some politicians, but until recently the threat of neonicotinoids to bees has not been seriously implicated in their decline. Concern about pollinator decline is a result of the important role that pollinators play in food production: 75% of crop species depend on animal pollinators, which translates into 35% of global production; and the total annual economic value of pollination has been estimated at €153 billion globally. In addition, pollinators are fundamental to most terrestrial ecosystems, and indirectly affect the availability of food for other organisms (e.g. fruits and berries for frugivorous birds), as well as the structure and functioning of ecosystems.

So here’s the paradox: flower-visiting insects including bees are really important for agricultural production. But so is the use of neonicotinoid pesticides. Which is more important and is the ban justified on scientific grounds?

In the last year, the evidence that neonicotinoids have negative impacts on bees has been mounting. Bees and other flower-visiting insects are exposed to neonicotinoid pesticides in multiple ways: during planting of seeds which have been coated with pesticides as a pre-planting treatment, by collecting pollen and nectar from the crop, and by foraging on non-crop plants which take the pesticide up through the soil. Traditionally, toxicological tests of agrochemicals are carried out on the managed honeybee Apis mellifera, and pesticides are rated according to their lethal effects (by calculating the LD50 – the dose required to kill half the organisms tested after a specified duration). But the biology of Apis and all the other bee species (20,000 of them worldwide) is different. Can we generalise about effects on Apis, to effects on other bee species, and other pollinating insects including hoverflies and butterflies? And what about sub-lethal effects, i.e. those that don’t kill the insects, but affect their physiolology, behaviour and fitness?

Neonicotinoids are highly toxic to insects – that’s the whole point of them. Bees are insects. So it shouldn’t be too much of a shock that they kill bees. Last year it was shown that neonicotinoids can also have sub-lethal effects in honeybees, by decreasing foraging success and navigation by individuals back to the hive. At the same time, the neonicotinoid pesticide, imidacloprid, can reduce bumblebee colony growth and fitness by affecting their feeding behaviour. Some dissenters have cast doubt on the field-relevance of laboratory tests, claiming that field-realistic dosages have not been used, but this is not the case – the concentration of imidacloprid in oilseed rape flowers for example has been found to be 4.4-7.6 mg/kg in pollen and 0.6-0.8 mg/kg in nectar, which was within the range tested on bumblebees. This is pretty convincing evidence that neonicotinoids can cause very adverse effects on populations of these social bees.

Although neonicotinoids are not the only cause of widespread bee decline, they are more than likely contributing to it. Some of the agrochemical companies are claiming that bee decline has nothing to do with their chemicals and instead blame decline on Varroa destructor, the parasitic mite which infects honeybee colonies. Whilst Varroa probably plays its part in honeybee decline, the most probable cause of decline in other bee species is multiple pressures, including habitat loss and loss of forage plants, AND the use of neonicotinoid pesticides.

So should these insecticides be banned? YES, if we want to address pollinator decline. They should not be used for insect-pollinated crops, and wind-pollinated crops that insects forage on (including maize). But what’s the alternative for the farmer? How can crop production be maintained in the absence of these chemicals? Use something worse? If we’ve learned anything since Rachel Carson’s “Silent Spring” published 50 years ago last year, it’s that an alternative will be found, and we can’t be sure that this won’t be worse for the bees and other pollinating insects.

Author

Jane Stout: stoutj@tcd.ie

Photo credit

wikimedia commons

20/02/2013

Sampling gaps in our understanding of primate parasites

*by parasites here I am referring to all kinds of infectious disease causing agents including bacteria, viruses, fungi, protozoa, helminths and arthropods.

Why do we care about primate parasites?

Many of the most devastating infectious diseases in humans have origins in wildlife. For example, the global AIDS pandemic originated through human contact with wild African primates and influenza viruses circulate among wild bird populations. These are not only historical occurrences. Recently, for example, rodents were identified as the source of a Hantavirus outbreak in Yosemite National Park, USA . As human populations continue to expand into new areas and global changes in temperature and habitat alter the distributions of wild animals, humans around the world will have greater contact with wildlife. Thus, understanding which infectious agents have the potential to spread from animals to humans is crucial for preventing future human disease outbreaks.

Many efforts are being made to collate information on wildlife and human diseases. Much of my research (which I will blog about when I get chance!) uses an amazing database known as the Global Mammal Parasite Database or GMPD for short. Every time a paper is published which contains details of parasites found in either primates, carnivores or ungulates, the information is added to the database. As much data as possible is recorded, including the species infected, the type of parasite, the prevalence of the parasite, and the geographic location of the study. Prof. Charles Nunn and his colleagues have been collecting data for the GMPD since around 2005 and it currently contains around 6000 records for primates alone. This definitely makes it the most comprehensive dataset of primate parasites in existence.

The GMPD sounds amazing…so what’s the problem?

The problem with the GMPD (and this is a feature of virtually all datasets) is that there is sampling bias. Certain primates are sampled for parasites much more frequently than others. Chimpanzees, for example, are sampled for parasites all the time, whereas species such as tarsiers are sampled much less often. This has the effect of making it look like chimpanzees have far more parasites than tarsiers, simply because they have been sampled more often. In analyses using the database we usually deal with this problem by adding sampling effort into our models, so we give less emphasis to high numbers of parasites in primates we have lots of samples for. Unfortunately this problem is also evident when we look at parasites (things like malarial parasites are often sampled because of their importance to human health) and geographic regions (areas with primate research stations are sampled far more regularly than more remote regions). If we hope to use the GMPD data to make reliable predictions about future risks to humans, we need to identify gaps in our knowledge of primate parasites.

So what did you do?

Without going into the technical details, we looked across the primate phylogeny and primate geographic ranges to identify gaps in our knowledge, and used statistical models to investigate what factors led to primates and geographic areas being relatively well- or relatively poorly-sampled. We also used species accumulation curves to extrapolate parasite species richness for primates.

Where are the gaps in our knowledge?

We found that apes (chimpanzees, gorillas and orangutans) were generally better-sampled than other primates, but there was incredible variation in sampling among all other major primate groups. Apart from apes, the primates that researchers appear to sample most are the species they encounter most often, i.e., widespread, terrestrial, diurnal species. However, some primates were sampled more often because they are already intensively studied for other research, because they live in frequently visited field sites, or because of their importance in medical research. Across countries, we found that in general, parasite sampling is highest in countries with more primates to sample. We expected that the GDP of the countries would also affect sampling effort, with wealthier countries having more money for disease monitoring. However, we found no evidence for this in our analyses, probably because most research on primate diseases is not funded by the country in which the research takes place.

Sampling effort for primate parasites across the world. Poorly-sampled countries are in red, and better sampled countries are in yellow.

When we extrapolated parasite species richness values we found that even within our best-sampled primates and countries, we are missing a lot of parasites. On average we predicted that 38-79% more parasite species than currently reported in the GMPD should be found in our best sampled primate species, and 29-40% more parasite species than currently reported in the GMPD should be found in our best sampled countries. This emphasizes exactly how poor our sampling is across all primates and countries. Another concern is that although viruses make up only 12% of the parasites in our dataset, viruses arguably present the greatest zoonotic disease threat to humans because their fast rates of evolution should allow them to easily adapt to new hosts.

What next?

Identifying parasite sampling gaps across primate species and geographic regions is only the first step; we need to find strategies to minimize these sampling gaps if we are to predict which primate diseases may emerge in humans. One solution is to set research priorities based on the sampling gaps, for example, by focusing effort and funding on relatively poorly-sampled primate species, arboreal primates, those with small geographic ranges, or those found in relatively poorly-sampled regions of South East Asia, Central and Western Africa, and South America.

Focusing on relatively poorly-sampled primate species and areas may improve our general understanding of primate parasites, but it is only one factor in predicting risk to humans. For example, hosts are more likely to share parasites with their close relatives than with more distant relatives. Thus, continuing to focus our sampling efforts on parasites of our closest relatives (chimpanzees, gorillas and orangutans) may provide the greatest return in the case of risks to humans. This is particularly important because we found that chimpanzees are expected to have 33-50% more parasites than currently found in the GMPD. In addition, ecological similarities also influence parasite sharing among primates, and humans share more parasites with terrestrial than arboreal primate species. As with sampling effort, this probably reflects higher contact rates among humans and terrestrial primates compared to arboreal primates. As a related issue, a host living at higher density is expected to have higher prevalence of parasites and may have more contact with human populations or our domesticated animals, thus increasing opportunities for host shifts to humans. The large numbers of zoonotic emerging infectious diseases with rodent or domesticated animal sources also highlight the importance of rates of contact and host density for disease emergence in humans.

In conclusion Sampling effort for primate parasites is uneven and low. The sobering message is that we know little about even the best studied primates, and even less regarding the spatial and temporal distribution of parasitism within species. Much more sampling is needed if we hope to predict or prevent future emerging infectious diseases outbreaks.

Author

Natalie Cooper

nhcooper123

ncooper[at]tcd.ie

Photo credit

Natalie Cooper, wikimedia commons