Recently Published in the Journal

An evolutionary perspective on the walking gait of the long-beaked echidna

Have you ever seen how echidnas walk? If so, you must have noticed their unusual walking gait. A paper published in Journal of Zoology investigates the evolutionary transition of mammalian locomotion from sprawling to parasagittal by examining the ‘transitional’ walking gait of long-beaked echidnas (Zaglossus bruijni). The paper contains a series of photographs of a walking echidna that perfectly illustrates how, instead of the diagonal, right-hand-moves-with-the-left-foot-and-vice-versa gait that we generally see in mammals, echidnas are yawing themselves from side to side in a more right-hand-moves-with-the-right-foot-etc fashion, which inevitably makes their walk look unusual and endearingly comical! Take a look at this great video, provided as online supplementary material with the paper, and you’ll see what I mean.

By Elina Rantanen

New Journal of Zoology Podcast

The spring 2013 episode of the Journal of Zoology Podcast is now online and you can listen to it here.

In this episode, Shannon Barber-Meyer tells us about tiger occupancy surveys and how they are used in tiger conservation, we learn from Megan Strauss how lion predation on giraffes can be studied by surveying for claw marks on live giraffes, we hear from Noriko Iwai about a Japanese ‘sumo-wrestling’ frog that use spines projecting from their hands in combat and mating, and Kate Umbers talks about the production and the functions of blue colouration in the animal world.

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By Elina Rantanen

2013 Thomas Henry Huxley Review

Social competition and its consequences in female mammals

Competition between females is one of the cornerstones of the theory of natural selection but the majority of studies on reproductive competition focus principally on mating competition in males.  The 2013 Thomas Henry Huxley Review, published in the Journal of Zoology, provides a fascinating summary of the adaptive tactics used by competing female social mammals and the social mechanisms that affect competitive success. 

Photo: Elise Huchard

The authors, Tim Clutton-Brock and Elise Huchard, explore a range of competitive strategies, including punishment and harassment, reproductive suppression, infanticide, eviction, kinship and dominance. Some intriguing elements of competition, such as female armaments and ornamentation, female masculinisation and sexual mimicry, are also described.  In some species, both the extent of reproductive skew and the intensity of selection on traits that enhance competitive success are greater in females than in males. However, overt fighting between females is not as common as among males and the development of sexually selected weaponry in females is rarely as extreme as in males.  Instead, females tend to use social strategies to enhance their reproductive success, which may explain why females are commonly more responsive than males to social signals and relationships.  Despite the presence of these differences, the underlying mechanisms affecting fitness in the two sexes are fundamentally similar. As in males, females compete to maintain exclusive access to resources and mates as well as to attract members of the opposite sex.  In recent years, the underlying similarity in the operation of selection in males and females has generated debate over whether or not reproductive competition between females should be regarded as a form of sexual selection or whether it should be allocated to some other category of selection, such as social.  Whichever approach is adopted, the existence of this discussion underlines the qualitative similarity in the evolutionary mechanisms operating in both sexes.

Linda DaVolls

Hidden Gem

Nopcsa, F. (1907) Ideas on the Origin of Flight. Proceedings of the Zoological Society of London, 77: 223-236.

This ‘hidden gem’ from 1907 is a wonderful specimen of natural history and early palaeontology which discusses the origin of flight in pterosaurs, mammals, dinosaurs and birds. The article, published in the Journal of Zoology’s predecessor Proceedings of the Zoological Society of London, is written by Dr Baron Francis, or Franz, Nopcsa, a Hungarian palaeontologist who supported the idea that birds evolved from dinosaurs, as first proposed by Thomas Henry Huxley. Dr Nopcsa begins his article by emphasising the essential difference between patagium and feather as the two structures used for flight in vertebrates, pointing out that “a patagium is a soft flexible membrane and in consequence requires, to be effective, numerous firm radial supports originating from the body that has to be carried, whereas for a series of semirigid but elastic quills one line of attachment is sufficient.” He observes how in pterosaurs and bats, both the fore and hind limbs as well as the tail have evolved to support the patagium, and concludes that “since the union of fore and hind limbs is directly opposed to bipedal cursorial locomotion, we can safely state that all patagium-flying animals originated from quadrupedal, leaping, arboreal forms”, whereas, inferring from the fossils of the oldest known bird Archaeopteryx, Dr Nopcsa proposes that “birds originated from bipedal long-tailed cursorial reptiles which during running oared along in the air by flapping their free anterior extremities.” The author then presents in a sketch his vision of a “Pro-avis”, a hypothetical, dinosaur-like bipedal reptile with horny scales on the fore limbs that would aid this creature to “take longs strides or leaps”, and which would “ultimately develop to actual feathers”. We hope you enjoy the free paper in the Hidden Gems section of the journal website.

By Elina Rantanen

Recently published in the Journal

Chemical defense of an Asian snake reflects local availability of toxic prey and hatchling diet

There are species of snakes that derive toxins from prey for their own defence against predators. Rhabdophis tigrinus is an oviparous Asian snake that has unusual defensive glands on the neck (nuchal glands), which typically contain toxic bufadienolide steroids that the snakes sequester from consumed toads. A paper published in Journal of Zoology  shows how this species may exhibit population-level variation in their chemical arsenal, reflecting the availability of chemically defended prey in their habitat. The study compared the chemistry of the nuchal gland fluid of R. tigrinus from two Japanese islands: Ishima, where toads are abundant, and Kinkasan, where toads are absent. The results showed that captive-hatched juveniles from toad-rich Ishima Island that had not been fed toads still possessed defensive bufadienolides in their nuchal glands, presumably due to maternal provisioning of these sequestered compounds. Wild-caught juveniles from Ishima also possessed large quantities of bufadienolides, which could result from a combination of sequestration of defensive compounds from consumed toads and maternal provisioning. Captive-born hatchlings from Kinkasan Island lack bufadienolides in their nuchal glands, reflecting the absence of toads on that island, but they can still sequester bufadienolides by feeding on toads in captivity.

It is likely that contact between the irritating nuchal gland fluid from these snakes and the eyes or mouth of its predators, such as raptors, giant salamanders, raccoondogs and other snakes, will serve as an effective deterrent.  Therefore, the presence of large quantities of bufadienolides in the nuchal glands of R. tigrinus on the Ishima Island could provide an effective chemical defence and deterrent against predators, whereas R. tigrinus on the toad-free Kinkasan Island may experience more intensive predation due to the lack of defensive compounds in their nuchal glands. Indeed, this is probably why the Kinkasan snakes typically flee from perceived predatory threats as they are less well defended against predator attacks.

by Linda DaVolls

New Journal of Zoology Podcast

The autumn 2012 episode of the Journal of Zoology podcast is now online and you can listen to it here.

In this episode, we learn from Thomas Hossie how prey adjust their anti-predator defences to variable levels of predation risk, Elodie Briefer talks about whether vocalisations could be used as indicators of animal emotions, we’ll hear about tracking leopards by GPS for modelling their predation behaviour from Ross Pitman, and Lisa Filippi tells us about a bug that calls its offspring to feed.

You may subscribe in iTunes to automatically receive the latest Journal of Zoology podcasts.

by Elina Rantanen

Home improvements: how transportable homes are incorporated into a population of hermit crabs

Homes for hermits: temporal, spatial and structural dynamics as transportable homes are incorporated into a population

Many animal populations are limited by the availability of life-sustaining resources.  A recent study by M.E. Laidre, published in the Journal of Zoology, explored the processes by which resources are incorporated into a population by introducing over one thousand transportable homes into a population of terrestrial hermit crabs Coenobita compressus.  The new homes were then tracked between years to test temporal, spatial and structural dynamics.  Because empty homes are rare, hermit crabs tend to interact (literally door-to-door) with conspecifics, forming large social aggregations in which many homes are swapped.  This was likely to be the cause of the rapid spike in traded-in homes once the introduced homes were discovered.  The exchange of homes was accelerated by the creation of vacancy chains, as crabs would drop off their old homes directly at the exchange site.  Traded-in homes tended to be under half the diameter of new homes. 

After moving to a new home the crabs would move away from the exchange site. The following year, these homes were displaced from the original exchange site by 0.23 ± 0.03 km (range: 0–2.41 km), thus penetrating extensively through the population. Crabs also remodeled the internal architecture by hollowing out the inside to create homes that were more spacious and less of a burden to carry. Remodeling may benefit the crabs, but it is unclear whether it constitutes a net home improvement as remodeled homes had thinner walls, potentially making them more susceptible to breakage or to being crushed by predators. More research is needed to understand how crabs balance these housing costs and benefits.  This interesting study suggests that transportable homes generate novel ecological dynamics along temporal, spatial and structural dimensions, which are a direct consequence of their transportability.

By Linda DaVolls