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  • Tags / Keywords Felis catus (Cat )
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  • Tags / Keywords fregetta grallaria
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Abundance and Home ranges of Feral Cats in an Urban Conservancy where there is Supplemental Feeding: a case study from South Africa
Island and Ocean Ecosystems, BRB
Available Online

Downs, C.T.

,

Tennent, J.

2008
There is much debate surrounding the impact of feral cats (Felis catus) on wildlife. Conservancies areusually areas where indigenous flora and fauna are protected and aliens excluded or managed. The University of KwaZulu-Natal’s Howard College campus (HCC) is an urban conservancy containing feral cats that are presently not managed, and little is known about their ecology and behaviour. Consequently a feral cat population census was conducted, and their home range investigated. Estimates of the overall campus feral cat population numbers ranged between 23.4–40.0 cats/km2 with a minimum of 55 identified as resident. They were not randomly distributed in the study area, with spacing patterns being related to resource availability. Home range area and core distribution of eight radio-collared cats were determined over 13 months. Total home range areas were relatively small, with considerable overlap between them. Home ranges were clustered in areas with permanent feeding stations and these were also within the cats’ core ranges. Supplemental food resources appear to have a major influence on numbers, home and core range area, and behavior of cats. It is clear that cat densities grow to high levels with reliable and abundant food supply and only ad hoc sterilization. This has implications for their management in the HCC urban conservancy.
The impacts of introduced house mice on the breeding success of nesting seabirds on Gough Island
BRB
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Bond, Alexander L.

,

Caravaggi, Anthony

,

Cooper, John

,

Cuthber, Richard J.

,

Ryan, Peter G.

2018
Invasive species are the main threat to island biodiversity; seabirds are particularly vulnerable and are one of the most threatened groups of birds. Gough Island, a UNESCO World Heritage Site in the South Atlantic Ocean, is an Important Bird and Biodiversity Area, and one of the most important seabird colonies globally. Invasive House Mice Mus musculus depredate eggs and chicks of most seabird species on the island, but the extent of their impact has not been quantified. We used field data and bootstrapped normal distributions to estimate breeding success and the number of surviving chicks for 10 seabird species on Gough Island, and compared estimates with those of analogous species from predator-free islands. We examined the effects of season and nest-site location on the breeding success of populations on Gough Island, predicting that the breeding success of Gough birds would be lower than that of analogues, particularly among small burrownesting species. We also predicted that winter-breeding species would exhibit lower breeding success than summer-breeding species, because mice have fewer alternative food sources in winter; and below-ground nesters would have lower breeding success than surface nesters, as below-ground species are smaller so their chicks are easier prey for mice. We did indeed find that seabirds on Gough Island had low breeding success compared with analogues, losing an estimated 1 739 000 (1 467 000–2 116 000) eggs/ chicks annually. Seven of the 10 focal species on Gough Island had particularly high chick mortality and may have been subject to intense mouse predation. Below-ground and winter breeders had lower breeding success than surface- and summer-breeders. MacGillivray’s Prion Pachyptila macgillivrayi, Atlantic Petrel Pterodroma incerta and Tristan Albatross Diomedea dabbenena are endemic or near-endemic to Gough Island and are likely to be driven to extinction if invasive mice are not removed.