Direct evidence implicates feral cat predation as the primary cause of failure of a mammal reintroduction programme

As evidence mounts that the feral Cat (Felis catus) is a significant threat to endemic Australian biodiversity and impedes reintroduction attempts, uncertainty remains about the impact a residual population of cats following control will have on a mammal reintroduction programme. Also, behavioural interactions between cats and their prey continue to be an area of interest. Within the framework of an ecosystem restoration project, we tested the hypotheses that successful reintroductions of some medium‐sized mammals are possible in locations where feral cats are controlled (but not eradicated) in the absence of European Red Fox (Vulpes vulpes), and that hare‐wallabies that dispersed from their release area are more vulnerable to cat predation compared with those that remain at the release site. We used radiotelemetry to monitor the survivorship and dispersal of 16 Rufous Hare‐wallabies (Lagorchestes hirsutus spp.) and 18 Banded Hare‐wallabies (Lagostrophus fasciatus fasciatus) reintroduced to four sites within Shark Bay, Western Australia. Nearly all foxes were removed and feral cats were subject to ongoing control that kept their indices low relative to prerelease levels. All monitored hare‐wallabies were killed by cats within eight and 10 months following release. Significant predation by feral cats was not immediate: most kills occurred in clusters, with periods of several months where no mortalities occurred. Once a hare‐wallaby was killed, however, predation continued until each population was eliminated. Animals remaining near their release site survived longer than those that dispersed. The aetiology of predation events observed offers new insights into patterns of feral cat behaviour and mammal releases. We propose a hypothesis that these intense per capita predation events may reflect a targeted hunting behaviour in individual feral cats. Even where feral cats are controlled, the outcome from consistent predation events will result in reintroduction failures. Managers considering the reintroduction of medium‐sized mammals in the presence of feral cats should, irrespective of concurrent cat control, consider the low probability of success. We advocate alternative approaches to cat‐baiting alone for the recovery of cat‐vulnerable mammals such as hare‐wallabies.     

Critical‐weight‐range marsupials in northern Australia are declining: a commentary on Fisher et al. (2014) ‘The current decline of tropical marsupials in Australia: is history repeating?’

Many mammal species are declining in parts of Australia's tropical savannas, for reasons that are not yet well defined. A recent paper (Fisher et al., 2014, Global Ecology and Biogeography, 23 , 181–190) suggested that the primary cause is predation by feral cats, with the main evidence presented being a purported over‐representation of small species amongst the marsupials that have contracted in range (‘small body size signifies high current extinction risk’). However, a review here of the information presented in that paper shows that no marsupial species smaller than 100 g has shown range contraction in northern Australia, and that most (15 of 17) declines are of species in the ‘critical weight range’ (35 g to 5.5 kg).     

Are we getting the full picture? Animal responses to camera traps and implications for predator studies

Camera trapping is widely used in ecological studies. It is often considered nonintrusive simply because animals are not captured or handled. However, the emission of light and sound from camera traps can be intrusive. We evaluated the daytime and nighttime behavioral responses of four mammalian predators to camera traps in road‐based, passive (no bait) surveys, in order to determine how this might affect ecological investigations. Wild dogs, European red foxes, feral cats, and spotted‐tailed quolls all exhibited behaviors indicating they noticed camera traps. Their recognition of camera traps was more likely when animals were approaching the device than if they were walking away from it. Some individuals of each species retreated from camera traps and some moved toward them, with negative behaviors slightly more common during the daytime. There was no consistent response to camera traps within species; both attraction and repulsion were observed. Camera trapping is clearly an intrusive sampling method for some individuals of some species. This may limit the utility of conclusions about animal behavior obtained from camera trapping. Similarly, it is possible that behavioral responses to camera traps could affect detection probabilities, introducing as yet unmeasured biases into camera trapping abundance surveys. These effects demand consideration when utilizing camera traps in ecological research and will ideally prompt further work to quantify associated biases in detection probabilities.     

Top-predator control-induced trophic cascades: an alternative hypothesis to the conclusion of Colman et al.

Colman et al. (2014 Proc. R. Soc. B 281, 20133094. (doi:10.1098/rspb.2013.3094)) recently argued that observed positive relationships between dingoes and small mammals were a result of top-down processes whereby lethal dingo control reduced dingoes and increased mesopredators and herbivores, which then suppressed small mammals. Here, I show that the prerequisite negative effects of dingo control on dingoes were not shown, and that the same positive relationships observed may simply represent well-known bottom-up processes whereby more generalist predators are found in places with more of their preferred prey. Identification of top-predator control-induced trophic cascades first requires demonstration of some actual effect of control on predators, typically possible only through manipulative experiments with the ability to identify cause and effect.     

Diet of free-ranging cats and dogs in a suburban and rural environment, south-eastern Brazil

In spite of the worldwide occurrence of domestic cats and dogs, and their close relationship with humans, the number of published papers on free-ranging cats Felis catus and dogs Canis familiaris , is small. The diet of both species was estimated in a suburban and rural environment in July 2002 and January 2003. Visual observations and scat collection of both species were accomplished along a 10 km transect line in the Campus 'Luiz de Queiroz', University of São Paulo, Piracicaba, south-eastern Brazil. The diet of both species was determined by analysis of sterilized, washed, dried and sorted scats. Estimated abundances of free-ranging cats and dogs in the sampled area were 81 (±4.32) and 42 (±2.96), respectively. Cats and dogs were more abundant in the suburban than in the rural environment ( t =3.78, P <0.001, N =55; t =8.38, P <0.001, N =55, respectively) and cats were more abundant than dogs in the suburban environment ( t =6.76, P <0.001, N =55), even though there was no significant difference between the abundance of both species in the rural environment ( t =0.82, P =0.46, N =55). Invertebrates were the most commonly consumed item by both species, followed by mammals (cats: 63.24 and 20.51%; dogs: 57.05 and 25.15%, respectively). Niche breadth was 0.4892 for cats and 0.4463 for dogs. Niche overlap was almost complete (0.97108). The consumption of mammals was estimated to be between 16.76 and 25.42 kg  individual⁻¹year⁻¹ for dogs and between 2.01 and 2.9 kg individual⁻¹year⁻¹ for cats. These data might be useful to establish a management program to minimize the predation pressure of free-ranging cats and dogs on wildlife.     

Heterochrony revisited: the evolution of developmental sequences

The concept of heterochrony is a persistent component of discussions about the way that evolution and development interact. Since the late 1970s heterochrony has been defined largely as developmental changes in the relationship of size and shape. This approach to heterochrony, here termed growth heterochrony, is limited in the way it can analyse change in the relative timing of developmental events in a number of respects. In particular, analytical techniques do not readily allow the study of changes in developmental events not characterized by size and shape parameters, or of many kinds of events in many taxa. I discuss here an alternative approach to heterochrony, termed sequence heterochrony, in which a developmental trajectory is conceptualized as a series of discrete events. Heterochrony is demonstrated when the sequence position of an event changes relative to other events in that sequence. I summarize several analytical techniques that allow the investigation of sequence heterochrony in phylogenetic contexts and also quantitatively. Finally, several examples of how this approach may be used to test hypotheses on the way development evolves are summarized.