Dataset Information

Devil declines and catastrophic cascades: is mesopredator release of feral cats inhibiting recovery of the eastern quoll?

ABSTRACT: The eastern quoll (Dasyurus viverrinus) is a medium-sized Australian marsupial carnivore that has recently undergone a rapid and severe population decline over the 10 years to 2009, with no sign of recovery. This decline has been linked to a period of unfavourable weather, but subsequent improved weather conditions have not been matched by quoll recovery. A recent study suggested another mechanism: that declines in Tasmanian devil (Sarcophilus harrisii) populations, due to the spread of the fatal Devil Facial Tumour Disease, have released feral cats (Felis catus) from competitive suppression, with eastern quoll declines linked to a subsequent increase in cat sightings. Yet current evidence of intraguild suppression among devils, cats and quolls is scant and equivocal. We therefore assessed the influences of top-down effects on abundance and activity patterns among devils, feral cats and eastern quolls. Between 2011 and 2013, we monitored four carnivore populations using longitudinal trapping and camera surveys, and performed camera surveys at 12 additional sites throughout the eastern quoll's range. We did not find evidence of a negative relationship between devil and cat abundance, nor of higher cat abundance in areas where devil populations had declined the longest. Cats did not appear to avoid devils spatially; however, there was evidence of temporal separation of cat and devil activity, with reduced separation and increasing nocturnal activity observed in areas where devils had declined the longest. Cats and quolls used the same areas, and there was no evidence that cat and quoll abundances were negatively related. Temporal overlap in observed cat and quoll activity was higher in summer than in winter, but this seasonal difference was unrelated to devil declines. We suggest that cats did not cause the recent quoll decline, but that predation of juvenile quolls by cats could be inhibiting low density quoll populations from recovering their former abundance through a 'predator pit' effect following weather-induced decline. Predation intensity could increase further should cats become increasingly nocturnal in response to devil declines.

SUBMITTER: Fancourt BA

PROVIDER: S-EPMC4356622 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Devil declines and catastrophic cascades: is mesopredator release of feral cats inhibiting recovery of the eastern quoll?

Fancourt Bronwyn A BA Hawkins Clare E CE Cameron Elissa Z EZ Jones Menna E ME Nicol Stewart C SC

PloS one 20150311 3

The eastern quoll (Dasyurus viverrinus) is a medium-sized Australian marsupial carnivore that has recently undergone a rapid and severe population decline over the 10 years to 2009, with no sign of recovery. This decline has been linked to a period of unfavourable weather, but subsequent improved weather conditions have not been matched by quoll recovery. A recent study suggested another mechanism: that declines in Tasmanian devil (Sarcophilus harrisii) populations, due to the spread of the fata ...[more]

PMID: 25760348

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Project description:Australia's native marsupial fauna has just two primarily flesh-eating 'hypercarnivores', the Tasmanian devil (Sarcophilus harrisii) and the spotted-tailed quoll (Dasyurus maculatus) which coexist only on the island of Tasmania. Devil populations are currently declining due to a fatal transmissible cancer. Our aim was to analyse the diet of both species across their range in Tasmania, as a basis for understanding how devil decline might affect the abundance and distribution of quolls through release from competition. We used faecal analysis to describe diets of one or both species at 13 sites across Tasmania. We compared diet composition and breadth between the two species, and tested for geographic patterns in diets related to rainfall and devil population decline. Dietary items were classified into 6 broad categories: large mammals (≥ 7.0kg), medium-sized mammals (0.5-6.9kg), small mammals (< 0.5kg), birds, reptiles and invertebrates. Diet overlap based on prey-size category was high. Quoll diets were broader than devils at all but one site. Devils consumed more large and medium-sized mammals and quolls more small mammals, reptiles and invertebrates. Medium-sized mammals (mainly Tasmanian pademelon Thylogale billardierii), followed by large mammals (mainly Bennett's wallaby Macropus rufogriseus) and birds, were the most important prey groups for both species. Diet composition varied across sites, suggesting that both species are flexible and opportunistic foragers, but was not related to rainfall for devils. Quolls included more large mammals but fewer small mammals and invertebrates in their diet in the eastern drier parts of Tasmania where devils have declined. This suggests that a competitive release of quolls may have occurred and the substantial decline of devils has provided more food in the large-mammal category for quolls, perhaps as increased scavenging opportunities. The high diet overlap suggests that if resources become limited in areas of high devil density, interspecific competition could occur.

Project description:BACKGROUND:Recombination is a relatively common phenomenon in retroviruses. We investigated recombination in Feline Immunodeficiency Virus from naturally-infected New Zealand domestic cats (Felis catus) by sequencing regions of the gag, pol and env genes. RESULTS:The occurrence of intragenic recombination was highest in env, with evidence of recombination in 6.4% (n = 156) of all cats. A further recombinant was identified in each of the gag (n = 48) and pol (n = 91) genes. Comparisons of phylogenetic trees across genes identified cases of incongruence, indicating intergenic recombination. Three (7.7%, n = 39) of these incongruencies were found to be significantly different using the Shimodaira-Hasegawa test.Surprisingly, our phylogenies from the gag and pol genes showed that no New Zealand sequences group with reference subtype C sequences within intrasubtype pairwise distances. Indeed, we find one and two distinct unknown subtype groups in gag and pol, respectively. These observations cause us to speculate that these New Zealand FIV strains have undergone several recombination events between subtype A parent strains and undefined unknown subtype strains, similar to the evolutionary history hypothesised for HIV-1 "subtype E".Endpoint dilution sequencing was used to confirm the consensus sequences of the putative recombinants and unknown subtype groups, providing evidence for the authenticity of these sequences. Endpoint dilution sequencing also resulted in the identification of a dual infection event in the env gene. In addition, an intrahost recombination event between variants of the same subtype in the pol gene was established. This is the first known example of naturally-occurring recombination in a cat with infection of the parent strains. CONCLUSION:Evidence of intragenic recombination in the gag, pol and env regions, and complex intergenic recombination, of FIV from naturally-infected domestic cats in New Zealand was found. Strains of unknown subtype were identified in all three gene regions. These results have implications for the use of the current FIV vaccine in New Zealand.

Dataset Information

Devil declines and catastrophic cascades: is mesopredator release of feral cats inhibiting recovery of the eastern quoll?

Publications

Devil declines and catastrophic cascades: is mesopredator release of feral cats inhibiting recovery of the eastern quoll?

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