Diet of feral cats in NZ forest

Fitzgerald, A. M., & Karl, B. J. (1979). Foods of feral house cats (Felis catus L.) in forest of the Orongorongo Valley, Wellington. New Zealand journal of zoology,6(1), 107-126.

The foods of feral house cats in forest in the Orongorongo Valley, Wellington, were studied over 3 years and related to the availability of prey. Some cats were trapped, tagged, and released, and could be identified individually by coat colour and pattern. The number of cats, estimated from live-trapping and sightings, was stable during the study. Examination of 677 scats revealed that mammals (rat, rabbit, opossum, mouse, and stoat, in descending order of importance) formed the bulk of the diet by weight. Remains of birds occurred in 12% of scats, but birds were estimated to form only 4.5% by weight of the diet. Insect fragments were present in many scats; wetas (Orthoptera), cicadas (Hemiptera), and beetles (Colcoptera) were important seasonally. Although eaten in large numbers, they contributed very little by weight to the diet. Populations of rats, rabbits, and opossums were fairly stable during the study; mice were abundant for most of the first 18 months, but were scarce in the last year. The literature on the food habits of feral house cats is reviewed; it emphasises that cats are primarily predators of small mammals (rodents and lagomorphs). Predation by feral cats can be important in holding rat and rabbit populations at low densities and in reducing seasonal fluctuations in their numbers. Cats can also exert heavy predation pressure on low-density mouse populations. Although the cats now eat few birds, they may have been responsible for reducing the numbers of some forest birds in the past.

How the Macquarie Island parakeet became extinct

Taylor, R. H. (1979). How the Macquarie Island parakeet became extinct. New Zealand Journal of Ecology, 2, 42-45.

For 70 years following the discovery of Macquarie Island in 1810 the endemic parakeet Cyanoramphus novaezelandiae erythrotis remained plentiful, despite the introduction of cats (Felis catus) and other predators. The crucial factor in the bird's rapid disappearance between 1881 and 1890 appears to have been the successful liberation of rabbits (Oryctolagus cuniculus) in 1879. This led to great increases of feral cats and introduced wekas (Gallirallus australis) and presumably to greatly intensified predation on parakeets.

Changes in numbers of parakeets, rats,mice, feral rabbits, feral dogs, feral cats and wekas on Macquarie Island 1810-1920. Diagrammatic reconstructionfrom early accounts (Cumpston, 1968). Not to scale.

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Dogs predating on green turtle nests

Fowler, L. E. (1979). Hatching success and nest predation in the green sea turtle, Chelonia mydas, at Tortuguero, Costa Rica. Ecology, 60 (5) 946-955.

Green turtle hatching success and nest predation were investigated at Tortuguero, Costa Rica, during July-November 1977. Forty-two percent of 350 study area nests and 57% of 237 beach survey nests produced emerging young; 38% and 24%, respectively, were destroyed by dogs, coatis, and vultures. The mean emergence percentage for the successful study area nests was 83%. About 13% of all eggs deposited did not hatch. A mean incubation period of 62 d and a mean clutch size of 104 eggs were recorded. Emergence success was not influenced by other recorded parameters (nest position on beach, rainfall, turtle's tag year, time of season, incubation period, and clutch size). Incubation period was related to nest position and clutch size. Dogs, coatis, and black and turkey vultures were the chief predators at Tortuguero; dogs did the most damage. Dogs and coatis found nests at all stages of development, but destroyed more nests containing hatchlings than nests containing unhatched eggs. Predation was related to nest position, but not to nest density. Nests were destroyed in equal proportion on the entire 35.4 km of beach. Predator activity was not consistent throughout the season; proportionally more nests were destroyed near the end of the nesting season than during the beginning.

Canis hybrids in Oklahoma

Freeman, R. C., & Shaw, J. H. (1979). Hybridization in Canis (Canidae) in Oklahoma. The Southwestern Naturalist, 24 (3) 485-499.

Fifteen cranial and dental measurements were taken from 138 wild Canis collected during 1975-76 and from 114 specimens collected from 1953-70. These were compared to known target populations of coyotes, red wolves, gray wolves, dogs, and coyote x dog hybrids by discriminant function and canonical variable analyses and were, along with weight and pelage color, used to assign each specimen. Measurements of current (1975-76) specimens were compared with those of older (1953-70) samples to test for temporal changes. Most current Oklahoma specimens were coyote-like, with 82.9 percent of the males and 78.6 percent of the females classified as coyotes. Evidence of coyote x dog hybridization was found in 14.6 and 10.7 percent of the males and females, respectively. Red wolf x coyote ancestry was evident in 2.4 percent of the males and 10.7 percent of the females. Temporal comparisons indicated consistent levels of hybridization except in southeastern Oklahoma, where red wolf influence is declining.

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Cat diet on several sub-Antarctic islands

Kerguelen
Pontier, D., L. Say, F. Debias, J. Bried, J. Thioulouse, T. Micol & E. Natoli. 2002. The diet of feral cats (Felis catus L.) at five sites on the Grande Terre, Kerguelen archipelago. Polar Biology, 25: 833–837
Assessing the impact (direct or indirect) of introduced predator species on native seabird populations is a clear management priority, particularly so in the simple sub-Antarctic ecosystems where these effects may be dramatic. We evaluated the diet of introduced feral cats (Felis catus L.) on the Grande Terre, Kerguelen archipelago, by analysing 149 scats from 5 sites. Overall, rabbits (Oryctolagus cuniculus) were the primary prey (72.6%), followed by house mice (Mus musculus) (11.6%) and birds (all species confounded, 14.9%). However, the proportions of the three prey species varied among sites, reflecting the spreading pattern of cats onto the Grande Terre. Birds were consumed much less frequently in this study (7.3%, all sites pooled but one) compared to a 1976 study in the same area (66.3%), suggesting that cats had a strong impact on the native avifauna

Marion
van Aarde, R.J. 1980. The diet and feeding behaviour of feral cats, Felis catus at Marion Island. South African Journal of Wildlife Research, 10:123-128.

Analyses of prey remains (n = 1 224) and stomach contents (n = 125) of feral domestic cats at Marion Island indicated that these exotic predators mainly feed on nocturnal burrow­ing petrels (fam. Procellariidae). Seasonality in their diet is discussed and predation rate on the various prey species seems to be a factor of availability rather than selection. An estimate of predation rate based on the energy requirements of the cat population and the caloric content of their most im­portant prey species suggested that a single cat kills approximately 213 petrels per year.

Auckland
Harper, G.A. 2010. Diet of feral cats on subantarctic Auckland Island. New Zealand Journal of Ecology, 34(2): 259-261
Feral cats were trapped and cat scats collected at Port Ross, Auckland Island, during two weeks in winter 2007. Eleven cats were caught and 40 scats collected, including from upland tussock areas. Cats’ diet predominantly consisted of birds (77.5% occurrence in scats) and mice (52.5% occurrence). The cats were relatively heavy and in good condition compared with other feral cats in New Zealand populations.

Macquarie
Jones, E. (1984). The feral cat on Macquarie Island. Tasmanian Naturalist, 79: 16-17

Domestic cats must have been taken to Macquarie Island soon after its discovery in 1810; feral cats were reported on the Island by 1820 (Debenham 1945). No records are available on the activities of these cats for the next 70 years, but the role of the feral cat as a predator of burrow-nesting petrels was then recognised by visitors to Macquarie Island such as Hamilton (1894), Burton (1900) and Mawson (1916) (the latter two in Cumpston 1968).
During 1974 I studied the diet of feral cats on Macquarie Island by a combination of scat and gut analysis, in an effort to determine their present ecological impact on the Island's fauna.

The percentage frequencies of the major food items found in 756 cat scats are presented in Table 1.

TABLE 1. Occurrence of major food items in 756 cat scats.

Food Item	Number of Seats	Percentage Frequency
Rabbit	619	81.9
Prion	220	29.1
White-headed Petrel	120	15.9
Mouse	33	4.4
Penguin	25	3.3
Rat	20	2.6
Weka	15	2.0

These results clearty indicate that rabbits, Antarctic Prions and White-headed Petrels were the major dietary items; other foods were less frequently eaten. The analysis of the gut contents of an additional 41 adult cats confirmed this finding but also indicated a seasonal change of diet during winter when less common food items such as wekas were eaten, and scavenging on dead elephant seals and penguins took place. Also, by the measurement of bone fragments it was found that 58% of the rabbits eaten weighed 200 - 300g, 23% weighed 300 - 600g, 8% weighed 600 - 1300g, and 11% weighed more than 1300g.

Cats were sighted and seats collected from all parts of the Island but densities were highest in areas of greatest prey abundance. It was estimated that in 1974 there were between 250 - 500 adult cats present and those cats collected were similar in size (mean weight of males 4518g; mean weight of females 2844g) to common domestic cats.

The ecological impact that these cats are now having on the fauna of Macquarie Island is difficult to assess, due to the other major ecological changes which have also taken place. However thei r depredations may still be affecting the less common species of petrels present.

Since most burrow-nesting petrels are absent from the Island during winter and the young rabbits have grown larger, the total amount of food available to the cats at this time is at a minimum. This winter food stress acts as a yearly limit to the cat population size and also causes the change in diet mentioned earlier. Thus if a major reduction in the rabbit population could be achieved, then this would cause a corresponding reduction in the cat population. The remaining cats would then become major predators of young rabbits in the following spring and summer and suppress the rate of increase of the rabbit population. However if rabbits were eliminated from Macquarie Island, feral cats would become rare.

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Campbell

Dilks, P.J. Observations on the food of feral cats on Campbell Island. New Zealand Journal of Ecology, 2: 64-66. 

Feral cats (Felis catus) are very scarce on Campbell Island (52 S, 169 E). Scats were collected during three summer visits and later examined. Norway rats (Rattus norvegicus) were much the most important prey, although birds and insects were also taken.