Previous Editorial Board Member’s Choice

15 02 2012

Philip Batemanby Philip Bateman

Secret lives of maned wolves (Chrysocyon brachyurus Illiger 1815): as revealed by GPS tracking collars.
L.F. Bandeira de Melo, M.A. Lima Sábata, E.M. Vaz Magni, R.J. Young & C.M. Coelho, 2007, J. Zoology 271: 27–36.

What is the difference between science and technology? Science is, of course, an objective method of discovery, and technology is what scientists use when applying the method to empirical discovery. Advances in science and technology tend to go hand in hand. Any new technological advance is soon used for empirical discovery, and new theories soon appear to manifest the required technology to test them. One technological advance that we now probably take much for granted in field-based zoology is that of collaring or otherwise tagging animals in order to track them, or discover their home ranges or territories. Whilst this used to mean radio-telemetry requiring constant triangulation to pinpoint the animal GPS technology now means that collars can provide us with even more information and on species that previously we knew very little about without disturbing the animals apart from initially putting the collar on them. Bandeiro de Melo and colleagues used GPS collars to track three maned wolves, a shy and nocturnal species about which very little was previously known, in a Brazilian savanna habitat. What I find appealing about this sort of study is that it gives us insights into, often quite basic, natural history and zoology of species that, while sometimes familiar to us for centuries we tantalisingly have known barely anything about. Discovering that maned wolf pairs have a strong bond, often sleeping very close to each other during the day, but hunt entirely separately, all of which has been learned from position data recorded every two hours by their collars, strikes me as being the 21st Century equivalent of the observations of the naturalists of the previous two, or more centuries, who had to rely on the technology of their eras but were filled with delight and excitement at what they found. People like David Douglas and John Kirk Townsend (who wrote of a naturalist‟s ecstatic delight at new discoveries) in North America and W.H. Hudson and Gilbert White (who identified new species of warbler with a small telescope and a keen ear and observation skills) in Britain. For me, it emphasises that we are the heirs of these pioneers of field studies of animal behaviour and that we have discoveries ahead of us, thanks to advances in technology, which may be as apparently simple as theirs but are just as exciting and satisfying.

Editorial Board Member’s Choice

28 10 2011

by Dina Dechmann

Effects of canine breakage on tiger survival, reproduction and human–tiger conflict

J. M. Goodrich, I. V. Seryodkin, D. G. Miquelle, L. L. Kerley, H. B. Quigley & M. G. Hornocker, 2011, J. Zoology, 285: 93-98

Teeth have always fascinated me. Because they are so essential for animals’ survival and also because of how intricately they show animals’ adaptation to their ecological niche as well as their personal history. Show me your teeth and I tell you who you are. And what better examples for this are there than the canines of a predator?

A few years ago I was working on Barro Colorado Island in Panama at the same time as another team was conducting a tracking study of ocelots. To catch the ocelots, the researchers set up traps in the forest, baited with a live chicken. One female very quickly figured this out and turned “trap happy”, to the great annoyance of the ocelot researchers who would have liked to catch some other ocelots, too, and to the great delight of the rest of the scientists on the island, who got to see the release of a wild ocelot. “Oreja” was very old and all her canines were broken – the easily accessible chickens were thus a welcome addition to her diet.

I know that broken and missing teeth can decrease the feeding efficiency of animals, ultimately even leading to their death (as the ocelot researchers on BCI also found). But I did not know that missing canines are thought to create problem animals, because they start hunting domesticated animals, and that missing teeth are even a criterion that is used to identify and sometimes cull potential problem animals. In the current Journal of Zoology issue researchers from Russia and the USA put this to the test.They investigated the reproductive success of highly endangered Amur tigers with and without missing or broken canines in the wild, and they assessed the number of individuals with missing or broken canines, killed because of human-tiger conflict. Their results are sobering AND encouraging: the proportion of tigers with missing teeth was the same in the control population as among the killed conflict tigers and both groups seem to have the same number of offspring. These results are congruent with those for African tigers and thus imply that culling large felids with missing teeth to prevent conflicts with humans does nothing but kill more animals from usually threatened species and that management measures have to be more differentiated.

Between being an interesting read on an interesting subject– tiger canines – and presenting an impressive sample size from an animal that is rare and extremely difficult to study, this paper is an excellent example for the ZSL’s motto on the journals front page: living conservation!

Oreja, our trap-happy old island ocelot, with no canines left at all may have been a special case. She was caught about a dozen times and in spite of her broken canines she never attacked anyone.

Editorial Board Member’s Choice

9 09 2011

by Elodie Briefer

Seasonal changes in sexual size dimorphism in northern chamois    

M. Rughetti & M. Festa-Bianchet, 2011, J. Zoology, 284:257–264

Sexual Size Dimorphism (SSD) refers to differences in body size between males and females. Among mammals, this phenomenon is common; males have been selected to be larger than females in order to compete with other males and gain access to females. This is especially true in polygynous species, such as most ungulates, in which competition to mate is very strong. However, gaining and maintaining a large body size is very costly for males.

Rughetti and Fiesta-Bianchet investigated the secret behind chamois SSD, by measuring both skeletal size and body mass of males at different times of the year. The costs associated with these two measures are quite different, skeletal size depending on growth rate during the first years of life, and body mass relying on muscle and fat accumulation in adult males. This study thus differs with most previous studies on SSD, which did not try to tease apart these two measures. Interestingly, the authors found that, even if males were 40% heavier than females at the beginning of the rut, this difference decreased to 4% after the rut. SSD in spring was mainly attributable to differences in skeletal size (5%).

These results clearly show that SSD in chamois results from a greater accumulation of muscles and fat in males than females before the reproductive season. Body mass increased quickly in males before the rut and decreased during this period, which is associated with an increase in energy expenditure and a concomitant decrease in foraging time in many mammals. Seasonal decreases in body mass seem to be common among ungulates, and goes up to 20-30% loss in fallow deer, bighorn sheep and mountain goats. However, chamois appear to be unique in that SSD during the rut results entirely from an accumulation of body fat and muscles tissues in males. Such seasonal SSD appears as a good strategy, because it prevents males from having to fulfil the high energetic requirements of maintaining a large body size over the winter.

Similar studies on other ungulates, in which variations throughout the year in both skeletal size and body mass are measured, could help us understanding the different reproductive strategies observed among ungulates and the costs associated with sexual dimorphism.

Previous Editorial Board Member’s Choice

9 08 2011

by Heike LutermannHeike Lutermann

Altered prevalence of raccoon roundworm (Baylisascaris procyonis) owing to manipulated contact rates of hosts
M.E. Gompper & A.N. Wright, 2005, J. Zoology, 266:215-219

Parasites and pathogens are an ubiquitous threat to organisms and can cause substantial reductions in reproductive success and survival of their hosts. Hence, they constitute a powerful selective agent. Transmission of parasites is a key process in host-parasite interaction and is often related to contact rates among hosts. However, such contact rates are difficult to assess and most studies and theoretical models have used population density of the host as a proxy for contact rates. In marked contrast, the study by Gompper and Wright manipulates actual contact rates in racoons (Procyon lotor) by providing food resources in either a clumped or dispersed manner and measures the associated infection with a common nematode parasite before and after manipulation. Clumped resources lead to drastic increases in infected individuals despite population densities being similar in both groups. Remote photography confirmed that this was probably due to higher contact rates among individuals that aggregated at clumped food sources. Their study illustrates that parasite transmission is not a simple density-depend process and hence models based on population density alone are rather over simplistic. Racoons have successfully exploited resources provided by humans such as rubbish dumps and this is associated with even higher parasite prevalence than in the rural population studied. These dramatic effects of human activity have staged a new host-parasite dynamic and it will be exciting to watch this evolution in action.

Previous Editorial Board Member’s Choice

17 06 2011

This Editorial Board Member’s Choice article was previously published on our old platform and we are pleased to display this on the blog.

Editorial Board Member’s Choice

by Lars Podsiadlowski

Genetics and animal domestication: new windows on an elusive process
K. Dobney and G. Larsen, 2006, J. Zoology, 269:261-271

The domestication of wild animals was not only a crucial achievement in human prehistory: starting with Darwin, it has also served as an illustration of the evolutionary changes which selection can cause. Even today, in the genomic age, artificial selection is an important topic in evolutionary biology. In this review, K. Dobney and G. Larsen summarise several important studies from past and present research and raise important questions for future work.

Darwin noticed the conspicuous morphological and physiological similarities between domesticated animals from different species – and the similarity of the morphological and physiological changes that domesticated animals have undergone relative to their wild counterparts, such as the appearance of dwarf and giant varieties, piebald colour and even floppy ears. Subsequent studies have demonstrated that complex genetic networks control almost every aspect of an organism, e.g. selection for behavioural traits also alters morphology: Belyaev’s fox-farm experiment, dating back to the 1950s, in which the previously undomesticated silver fox was selected for tameness, led him to suggest that tiny genetic changes affecting the balance of hormones and neurochemicals may be the cause for some of the characters shared in various domesticated mammalian species: fascinatingly, a suite of characters not selected for, including piebald coats and dropping ears, also appeared in the foxes. Probably, comparative genomic and transcriptional analyses of domesticated animals and their wild counterparts will provide more and more important insights into the developmental and genomic control of morphological and behavioural changes in general.

Dobney and Larsen’s review addresses another important issue in the reconstruction of the history of domestication for individual species. The time and place of domestication and the wild ancestors of domesticated animals can now be estimated with molecular data. However, the authors also demonstrate that some results, like the dating of domestication with molecular clocks, have to be interpreted with caution. Complex histories of domestication are revealed in some studies with dogs and cattle, and many questions are still unresolved, requiring larger datasets of different genomic sources (and probably also from ancient samples).

All in all this is an excellent review, illuminating many different aspects of the biology of domestication and giving a broad overview of the relevant literature. In addition the authors provide important hints to open questions and further topics to be studied in this field. It is apparent that many results of modern domestication research may serve as good models in understanding fundamental principles of evolution – just as they did in Darwin’s time.

Editorial Board Member’s Choice

8 03 2011

Dina Dechmannby Dina Dechmann

Climate variability affects the impact of parasitic flies on Argentinean forest birds
L.R. Antoniazzi, D.E. Manzoli, D. Rohrmann, M.J. Saravia, L. Silvestri & P.M. Beldomenico, 2011, J. of Zoology 283: 126-134

During my PhD I worked on tropical bats that excavate and inhabit live termite nests and one of the conclusions I drew from my data was that high and stable temperatures inside the termite nests was a major reason justifying this time and energy consuming roost choice. However, almost every time I presented these data there was at least one critical voice in the audience doubting that the temperature difference I found (about 2 degrees Celsius more than maximum ambient temperature) would make a difference for an animal in the tropics “where it’s hot anyway”.

This paper by a group of collaborators from Argentina and the US does not investigate a tropical system, but a Pampean temperate one. However, the study was conducted during the local spring and summer when it’s either “hot” or “even hotter”. Looking at an impressively large number of bird species as well as nests they found an important effect of climate, precipitation and temperature on bot fly infestation of nestlings, particularly in passeriforms. This in turn significantly influenced nestling mortality. In other words, higher temperature and more rain meant higher parasite infestation and nestling mortality.

Climate change is expected to result in stronger temperature changes in regions at mid- to high-latitudes and those are the regions studied most intensively for predicting the effects of climate change. However, recent work beautifully exemplified by a paper published in Nature last year by Dillon, Wang and Huey, shows that this may be a dangerous approach. Ectotherms that live at low latitudes are also adapted to more narrow temperature ranges and consequently, much smaller temperature changes have much stronger effects here. Studies like the one published last month in Journal of Zoology by Antoniazzi and co-authors, indicate that this may also be true for warm blooded vertebrates and I concur with the authors that many more studies are needed to understand and predict the effects that climate change may have on these climatic regions that are so important for global biodiversity.

Editorial Board Member’s Choice

10 02 2011

Anthony Herrelby Anthony Herrel

Feeding biomechanics in the Great Barracuda during ontogeny
M. L. Habegger, P. J. Motta, D. R. Huber and S. M. Deban, 2011, J. Zoology, 283: 63-72

Many among us will probably still remember our days as ungainly clumsy teenagers with bodies growing faster than our nervous system can keep up with. Although the frustration of dealing with growth can cause a few embarrassing moments in the life of a teenager, for many animals, growth and the associated changes in body proportions are something they have to deal with for most of their life. And the consequences of failure are far greater than the few moments of embarrassment we may still remember from our own childhood.

The paper by Maria Laura Habegger is a nice example of a study exploring the effects of growth on bite force, an ecologically relevant and important trait for survival, especially if you’re a barracuda. Fish are different from mammals like us in more than one way. Not only do they have to deal with many fold greater viscosity and density of the medium they live in, but fish, like other most other ectotherms, continue to grow throughout their lives.  So why is it that growing can be such a nuisance? Simply put, the changes in mass of the body segments during growth are far greater than the changes in force muscles can generate, thus affecting the speed of movement by which animals can move their limbs or their jaws. Add to that the changes in neural control needed to deal with the changes in the mechanics, and opportunities for failure lurk behind every corner.

So how do fish like barracuda deal with growth while being dependent on the functioning of their feeding system to assure their next tasty morsel.  Based on careful dissections, biomechanical models, and an investigation of how muscles are activated during feeding, Habegger and colleagues show that barracudas are able to maintain a similar bite force for their body size throughout much of their life. Although in other fish size-related changes in feeding mechanics often lead to changes in diet during growth, barracudas are faithful to their diet. Consequently, keeping the growth of the jaw muscles up with changes in body size suffices to ensnare a bite of fish the next size up from last month’s one. The ram-based feeding strategy where the fish use their body to power them through the water towards the prey, rather than relying on suction feeding, also helps maintain the ability of these predators to catch elusive prey like fish throughout their lives. Add to that the intricate rotation of the upper jaw bones and the razor-sharp teeth and the success of barracuda as top predators in their ecosystem becomes obvious. And surprisingly enough, barracudas don’t have a big bite, sharp teeth and powerful ram feeding are apparently all you need if you like sushi.