Stray dogs den close to humans

Majumder, S. S., Paul, M., Sau, S., & Bhadra, A. (2016). Denning habits of free-ranging dogs reveal preference for human proximity. Scientific Reports, 6, 32014.

Dens are crucial in the early development of many mammals, making den site selection an important component of parental care in such species. Resource availability and shelter from predators primarily govern den selection. Species inhabiting human-dominated landscapes typically den away from human disturbance, often shifting dens to avoid humans during the early life of their young. Domesticated dogs have evolved in human proximity over centuries, being bred and reared in human homes for generations. While pets rely on their owners for shelter and care, free-ranging dogs roam uncared, and typically whelp in dens. We conducted a study on 148 free-ranging dog dens in India to understand their denning habits. Distance from resources influenced den choice, but anthropogenic disturbance did not. Dens were found in areas of high human activity, and begging from humans was preferred over scavenging. A study on 15 pregnant females revealed that females actively searched for denning sites, rejecting several intermediate ones before selecting the final den. We propose that the obvious preference of dogs for denning close to humans is a behavioural adaptation that helps them to survive in the urban landscape, in spite of the high human induced mortality during the early life of pups.

Vulture declines and increased dog scavenging

Ogada, D. L., Torchin, M. E., Kinnaird, M. F., & Ezenwa, V. O. (2012). Effects of vulture declines on facultative scavengers and potential implications for mammalian disease transmission. Conservation Biology, 26(3), 453-460.

Vultures (Accipitridae and Cathartidae) are the only known obligate scavengers. They feed on rotting carcasses and are the most threatened avian functional group in the world. Possible effects of vulture declines include longer persistence of carcasses and increasing abundance of and contact between facultative scavengers at these carcasses. These changes could increase rates of transmission of infectious diseases, with carcasses serving as hubs of infection. To evaluate these possibilities, we conducted a series of observations and experimental tests of the effects of vulture extirpation on decomposition rates of livestock carcasses and mammalian scavengers in Kenya. We examined whether the absence of vultures changed carcass decomposition time, number of mammalian scavengers visiting carcasses, time spent by mammals at carcasses, and potential for disease transmission at carcasses (measured by changes in intraspecific contact rates). In the absence of vultures, mean carcass decomposition rates nearly tripled. Furthermore, the mean number of mammals at carcasses increased 3-fold (from 1.5 to 4.4 individuals/carcass), and the average time spent by mammals at carcasses increased almost 3-fold (from 55 min to 143 min). There was a nearly 3-fold increase in the mean number of contacts between mammalian scavengers at carcasses without vultures. These results highlight the role of vultures in carcass decomposition and level of contact among mammalian scavengers. In combination, our findings lead us to hypothesize that changes in vulture abundance may affect patterns of disease transmission among mammalian carnivores.

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Los buitres (Accipitridae y Cathartidae) son los únicos carroñeros obligados que se conocen. Se alimentan de cadáveres en descomposición y son el grupo funcional de aves más amenazado del mundo. Los efectos posibles de las declinaciones de buitres incluyen una mayor persistencia de cadáveres y el incremento de la abundancia de y contacto entre carroñeros facultativos en esos cadáveres. Estos cambios podrían incrementar las tasas de transmisión de enfermedades infecciosas, con los cadáveres funcionando como focos de infección. Para evaluar estas posibilidades, realizamos una serie de observaciones y pruebas experimentales de los efectos de la extirpación de buitres sobre las tasas de descomposición de cadáveres de ganado y mamíferos carroñeros en Kenia. Examinamos sí la ausencia de buitres cambiaba el tiempo de descomposición de cadáveres, el número de mamíferos carroñeros visitando los cadáveres, el tiempo utilizado por mamíferos en los cadáveres y la potencial transmisión de enfermedades en los cadáveres (medida por cambios en las tasas de contacto interespecífico). En ausencia de buitres, las tasas medias de descomposición de cadáveres incrementaron 3 veces (de 1.5 a 4.4 individuos/cadáver), y el tiempo promedio invertido por mamíferos en los cadáveres incrementó casi 3 veces (de 55 min a 143 min). Hubo un aumento de casi tres veces en el número promedio de contactos entre mamíferos carroñeros en cadáveres sin buitres. Estos resultados resaltan el papel de los buitres en la descomposición de cadáveres y del nivel de contacto entre mamíferos carroñeros. En combinación, nuestros resultados nos llevaron a plantear la hipótesis de que cambios en la abundancia de buitre pueden afectar los patrones de transmisión de enfermedades entre mamíferos carnívoros.

Do scavenging dogs still prefer meat?

Bhadra, A., Bhattacharjee, D., Paul, M., Singh, A., Gade, P. R., Shrestha, P., & Bhadra, A. (2015). The meat of the matter: a rule of thumb for scavenging dogs?. Ethology Ecology & Evolution, 1-14.

Animals that scavenge in and around human settlements need to utilise a broad range of resources, and thus generalist scavengers are likely to be better adapted to human-dominated habitats. In India, free-ranging dogs (Canis lupus familiaris) live in close proximity with humans in diverse habitats, from forest fringes to metropolises, and are heavily dependent on humans for their food. It has been argued that the ability to digest carbohydrates was one of the driving forces for dog domestication. Though dogs are better adapted to digest carbohydrates than other canids, pet dogs show a clear preference for animal proteins. Our observations on streets of urban and semi-urban localities show that the free-ranging dogs are scavengers which primarily receive carbohydrate-rich food from humans. Their source for animal protein is typically garbage bins and leftovers, and such resources are rare. Using a series of field-based experiments, we test if the free-ranging dogs have adapted to a generalist scavenging lifestyle by losing preference for animal protein. Our experiments show that the free-ranging dogs, which are descendants of the decidedly carnivorous gray wolf (Canis lupus lupus), have retained a clear preference for meat, which is manifested by their choice of anything that smells of meat, irrespective of the actual nutrient content. The plasticity in their diet probably fosters efficient scavenging in a competitive environment, while a rule of thumb for preferentially acquiring specific nutrients enables them to sequester proteins from the carbohydrate-dominated environment.

Vulture-canid competition

Campbell, M. (2015). Biodiversity and Vulture-Canid Relations. J Biodivers Endanger Species, 3, e122.

Conclusions
The evidence hints that the more eagle-like Old World vultures have a more equal relationship than the New World vultures with scavenging canids. Further study on this difference is important for three reasons. Vultures have declined in many Eurasian and African countries and canids (including feral dogs) have increased their scavenging role. Hence, a vulture population recovery must acknowledge the competitive role of canids. Also, as condor recovery programs are gathering ground in the Americas, the coyotes are possible impediments, possibly to a greater degree than jackals would be to old world vultures. Canids have a strong sense of smell and may precede vultures at hidden carcasses (condors and Old World vultures lack a sense of smell), hence when more visible carcasses are removed for sanitation purposes, conflicts may emerge between vultures and canids over the few remaining food sources. This encourages possibilities for detailed field research, which may increase our knowledge of the ecological relations of vultures and link the somewhat disparate studies of vulture evolution and biology with ecology and conservation possibilities.

Limited capacity of anthropophilous scavengers to compensate loss of raptors

Huijbers, C. M., Schlacher, T. A., Schoeman, D. S., Olds, A. D., Weston, M. A., & Connolly, R. M. (2014). Limited functional redundancy in vertebrate scavenger guilds fails to compensate for the loss of raptors from urbanized sandy beaches. Diversity and Distributions.

Aim
Globally, urbanization is one of the most widespread, intense and ecologically destructive forms of landscape transformation, and it is often concentrated in coastal areas. Theoretically, species losses attributable to urbanization are predicted not to alter overall ecosystem function if functional redundancy (i.e. replacement of function by alternative species) compensates for such losses. Here, we test this expectation by measuring how coastal urbanization affects scavenger guilds on sandy beaches and whether changes in guild composition result either in an overall loss of scavenging efficiency, or in functional compensation under alternative guild structures, maintaining net ecosystem functioning.

Location
Fourteen beaches along the east coast of Australia with variable levels of urbanization.

Methods
Scavenging communities and rates of carrion removal were determined using motion-triggered cameras at the beach-dune interface.

Results
A substantial shift in the community structure of vertebrate scavengers was associated with gradients in urbanization. Iconic and functionally important raptors declined precipitously in abundance on urban beaches. Importantly, other vertebrates usually associated with urban settings (e.g. dogs, foxes, corvids) did not functionally replace raptors. In areas where < 15% of the abutting land had been developed into urban areas, carcass removal by scavengers was often complete, but always > 70%. Conversely, on beaches bordering coastal cities with < 40% of natural vegetation remaining, two-thirds of fish carcasses remained uneaten by scavengers. Raptors removed 70–100% of all deployed fish carcasses from beaches with < 8% urban land cover, but this number dropped significantly with greater levels of urbanization and was not compensated by other scavenger species in urban settings.

Main conclusions
There is limited functional redundancy in vertebrate scavenger communities of sandy beach ecosystems, which impacts the system's capacity to mitigate the ecological consequences of detrimental landscape transformations.

Ecology of the feral cat on Macquarie Island

Jones, E. (1977). Ecology of the feral cat, Felis catus (L.),(Carnivora: Felidae) on Macquarie Island. Wildlife Research, 4(3), 249-262.

On Macquarie Island from December 1973 to March 1975 the diet of feral domestic cats (Felis catus) was estimated. There was rabbit (Oryctolagus cuniculus) in 82% of faeces and 71% of guts, rabbits under 600 g bodyweight, about 10 weeks old, were 81% of all rabbits eaten. There were Antarctic prion (Pachyptila desolata) and white-headed petrel (Pterodroma lessonii). Cats ate small numbers of rats, mice and wekas and scavenged on dead elephant seals and penguins, especially in winter. Availability of food in winter seemed to be an important factor limiting the population; adult population was estimated to be 250 to 500 and the area of the island is 120 km². Prion and white-headed petrel nest in burrows; there was little or no predation by cats on surface nesters such as albatross, giant petrel, southern skua or southern black-backed gull, or on live penguin.

Dog scavenging sea-turtle nests

Ruiz‐Izaguirre, E., Woersem, A., Eilers, K., Wieren, S. E., Bosch, G., Zijpp, A. J., & Boer, I. J. M. (2014). Roaming characteristics and feeding practices of village dogs scavenging sea‐turtle nests. Animal Conservation.

Village dogs are reported to prey on sea-turtle nests at various beaches worldwide. Sea-turtle species present in Mexico include six species, which are listed under the International Union for Conservation of Nature Red List. It is however not clear why dogs scavenge and how they enter nesting areas; this hinders effective management of dogs at sea-turtle nesting beaches. Hunger, for example, could be a driving factor for village dogs to scavenge sea-turtle nests. The aim of this study was to gain insight into roaming characteristics and feeding practices of dogs scavenging sea-turtle nests. Movements of 19 village dogs (9 nest scavengers and 10 non-nest scavengers) at Colola village and beach (an important nesting ground for the eastern Pacific green turtle: Chelonia mydas) were monitored through radio-tracking and direct observations. A prerequisite for nest scavenging is traveling to the beach. We computed ‘distance from home to beach’ and ‘the activity range’ of nest scavengers and non-nest scavengers. Furthermore, the dogs' owners were interviewed regarding feeding practices. Nest scavengers had a lower metabolic energy intake of their daily food corn tortillas (296 kJ kg⁻¹ BW^0.75) than non-nest scavengers (464 kJ kg⁻¹ BW^0.75) (two-sample t-test=2.67, P=0.017). Moreover, 39% of owners reported that they provided turtle eggs or egg shells to their dogs at least once. The activity range of nest scavengers was significantly larger than that of non-nest scavengers (F=11.64, P=0.007). Dogs were generally found at the beach at night (42%) and dawn (34%). Our findings have implications for the management of dogs at sea-turtle nesting beaches. We recommend that dogs' movements should be restricted between night (09:00 pm) and dawn (06:00 am) and that sufficient and adequate feeding of dogs should be promoted among dog owners.

Scavenging by Wild Dogs, Red Foxes and Feral Cats in South-Eastern Australia

Forsyth, D. M., Woodford, L., Moloney, P. D., Hampton, J. O., Woolnough, A. P., & Tucker, M. (2014). How Does a Carnivore Guild Utilise a Substantial but Unpredictable Anthropogenic Food Source? Scavenging on Hunter-Shot Ungulate Carcasses by Wild Dogs/Dingoes, Red Foxes and Feral Cats in South-Eastern Australia Revealed by Camera Traps. PloS one, 9(6), e97937.

There is much interest in understanding how anthropogenic food resources subsidise carnivore populations. Carcasses of hunter-shot ungulates are a potentially substantial food source for mammalian carnivores. The sambar deer (Rusa unicolor) is a large (≥150 kg) exotic ungulate that can be hunted throughout the year in south-eastern Australia, and hunters are not required to remove or bury carcasses. We investigated how wild dogs/dingoes and their hybrids (Canis lupus familiaris/dingo), red foxes (Vulpes vulpes) and feral cats (Felis catus) utilised sambar deer carcasses during the peak hunting seasons (i.e. winter and spring). We placed carcasses at 1-km intervals along each of six transects that extended 4-km into forest from farm boundaries. Visits to carcasses were monitored using camera traps, and the rate of change in edible biomass estimated at ~14-day intervals. Wild dogs and foxes fed on 70% and 60% of 30 carcasses, respectively, but feral cats seldom (10%) fed on carcasses. Spatial and temporal patterns of visits to carcasses were consistent with the hypothesis that foxes avoid wild dogs. Wild dog activity peaked at carcasses 2 and 3 km from farms, a likely legacy of wild dog control, whereas fox activity peaked at carcasses 0 and 4 km from farms. Wild dog activity peaked at dawn and dusk, whereas nearly all fox activity occurred after dusk and before dawn. Neither wild dogs nor foxes remained at carcasses for long periods and the amount of feeding activity by either species was a less important predictor of the loss of edible biomass than season. Reasons for the low impacts of wild dogs and foxes on sambar deer carcass biomass include the spatially and temporally unpredictable distribution of carcasses in the landscape, the rapid rate of edible biomass decomposition in warm periods, low wild dog densities and the availability of alternative food resources.

Vulture decline and stray dogs' rise in India

The vulture population in India has gone from 40 million to 60,000 largely due to poisoning, often by the drug diclofenac. Carrion-consuming birds are now on the critically endangered list of BirdLife International, a global network of conservation groups. The result is an abundance of carcasses left untouched by vultures bringing in a whole host of new scavengers in ever increasing numbers, such as rats, stray dogs etc.. The new scavengers are less effective in clearing up the carcasses or removing disease from them in comparison to vultures. There is an increased risk of diseases such as tuberculosis, anthrax and foot-and-mouth disease as flesh is left on the bone when dogs scavenge from cows. Packs of dogs are now reported to be 'hunting' humans as well as wildlife and bring with them the threat of rabies. The increase in the number of feral dogs has seen India's human infection rate with rabies reach a world record level, over 20,000 deaths per year. Such is the problem; a plan to sterilize 8 million dogs over a decade has been introduced.

The Parsis of India who practice Zoroastrianism rely on vultures to dispose of their dead as their faith prevents them from burying, burning or submerging them due to fears over hygiene. Corpses are seen in the faith as impure so it contradicts their faith to allow anything that would defile the elements to enter into them. Bodies are laid out in the open for the vultures to consume and this can usually be done (to the bone) in around an hour by a large group of vultures. The practice has existed for centuries. Plummeting vulture populations mean half consumed bodies now lie for days leading to further risk of infection in the neighbouring communities, and ultimately encouraging a taste for human flesh amongst the ever increasing feral dog population. Attacks on humans in Bikaner in western Rajasthan state have rocketed with 1,000 dogs roaming the area. The farming community who have long been unaccustomed to dealing with carcasses have not been quick to adapt and this has exacerbated the problem. Lacking money and resources not to mention experience, they have been unable to dispose of bodies quickly and efficiently. Water contamination is also a worry for authorities as rotting meat degrades and enters the water table. In a country where water is a scarce and valued resource this has potentially dire consequences. 

Vulture decline costs in India

Markandya, A., T. Taylor, A. Longo, M.N. Murty, S. Murty & K. Dhavala. 2008. Counting the cost of vulture decline—An appraisal of the human health and other benefits of vultures in India. Ecological Economics, 67 (2): 194–204

Widespread use of the non-steroidal anti-inflammatory drug (NSAID) diclofenac to treat livestock has resulted in dramatic declines in the populations of vultures across India. This has become an issue of considerable concern as vultures are a keystone species and their decline has a range of socio-economic, as well as cultural and biodiversity impacts. In this paper, we review these impacts and estimate in detail the economic cost of one of them: the human health impacts of the vulture decline. Livestock carcasses provide the main food supply for vultures, and are also eaten by dogs. Dogs are the main source of rabies in humans in India, and their populations have increased substantially in parallel with the vulture decline. The potential human health impact of rabies associated with the vulture decline is found to be significant. This, and a wide range of other impacts suggest that significant resources should be put into (1) testing of pharmaceutical products to ensure that similar situations are not repeated, (2) helping vulture populations to recover through the use of alternative drugs to diclofenac that are of low toxicity to vultures, and (3) through conservation breeding programmes.

Cats on Dassen Island

Apps, P. 1984. Cats on Dassen Island. Acta Zool. Fennica, 172: 115-116.

Dassen Island, a small island off the west coast of South Africa, is an important nesting site for sea birds. Introduced mammals include Felis catus and Oryctolagus cuniculus. Studies on the ecological impact of the feral cat population showed that birds and rabbits contributed almost equally to the diet of the cats, but that most of the birds were scavenged, so that the impact of cat predation on their populations was insignificant, while rabbits were hunted and the effect may have been ecologically important. The cats' ecological role was influenced strongly by their behaviour, which must be considered in the planning of conservation or control measures.

Potential threats of domestic dogs to wild animals in fragmented Atlantic forest

Martinez, E.; C. Cesário; I. de Oliveira e Silva; V. Boere. 2013. Domestic dogs in rural area of fragmented Atlantic Forest: potential threats to wild animals. Ciencia Rural, 43 (11)

Domestic dogs' skills such as hunting and herding shifted as man migrated from rural areas to developing urban centers and led to a change in human-dog relationship and in the purpose of these animals in the properties. The countryside of Viçosa is characterized by small coffee farms surrounded by borders with fragments from the Brazilian Atlantic Forest. The close proximity of these environments favors the encounter between domestic and wild animals which may lead to dog attacks to wild animals and, consequently, disease transmission. The aim of this study was to understand the role of dogs in the rural environment and assess the possible risks they offer to native fauna. The data were obtained from structured questionnaires answered by dogs' owners from rural Viçosa. Results regarding the socioeconomic status of the owners revealed that the majority belonged to either the middle class or low educational level categories. In addition, it was observed that there is a preference for male dogs due to its guard activity and that most dogs live unconstrained. Even though most dogs are provided with good food management, 58% of them prey on wildlife. However, more than half of the dogs do not consume their prey which can be explained by the inherited ability of artificial selection but 36.5% of them have scavenger diet. Most of the dogs were immunized against rabies, whereas, only 28.8% were immunized against infectious diseases such as leptospirosis, distemper and parvovirus. In conclusion, the management of dogs by rural owners, mainly unrestrained living, and allied to inadequate vaccination coverage suggest that dogs are predators of Viçosa's rural wildlife and potential disseminators of disease.

Vulture awareness day

On the International Vulture Awareness Day, it's worth to mention the impact of feral and stray dogs on vultures arround the world, outcompiting and even predating on them.

Dog outcompete vultures at sea lion colony

Pavés, H. J., Schlatter, R. P., & Espinoza, C. I. (2008). Scavenging and predation by Black Vultures Coragyps atratus at a South American sea lion breeding colony. Vulture News, 58(1), 4-15.

Many animal species benefit from resources provided by other species. Such species may develop or coevolve particular interspecific relationships (for example: competition, depredation and mutualism). During two sea lion breeding seasons (1996-97 and 1997- 98), we observed behavioral interactions at the Punta Lobería Southern Sea-lion Otaria flavescens colony. We documented facultative mutualism, commensalism and depredation by Black Vulture Coragyps atratus, Kelp Gull Larus dominicanus and Domestic Dogs Canis familiaris on sea lions. Competitive relationships between Black Vulture and dogs were observed. We recorded depredatory behaviour by vultures on live seal pups. Black Vultures were the dominant bird consumer on carcasses in the absence of feral dogs. Sea lion mother displayed agonistically when Black Vultures approached their pups. Vultures fed on sea lion placentas and umbilical cords during the birth period. 12-17% of the sea lion pups suffered attacks by Black Vultures during our two season's observations. Dogs compete advantageously with vultures on seal pup carcasses. We postulate that the shift
from mutualistic scavenging to depredation by vultures may be influenced by hunger stress due to competition with feral dogs for limited sea lion carrion.


Distintas especies de animales se asocian y benefician de los recursos generados en una colonia reproductiva de lobo marino común (Otaria flavescens), desarrollando un conjunto de relaciones interespecíficas coevolutivas particulares (competencia, depredación, mutualismo, entre otros). Durante dos periodos reproductivos (1996-1997 y 1997-1998) se realizaron observaciones de las conductas interespecíficas en la colonia reproductiva de Punta Lobería (38º39'S; 73º29'W). Se registraron relaciones de tipo mutualista, comensal y depredadoras, entre Jote cabeza negra (Coragyps atratus), Gaviota dominicana (Larus dominicanus) y Perros domésticos abandonados (Canis familiaris) sobre O. flavescens. Relaciones competitivas entre Jote cabeza negra, Jote de cabeza colorada (Cathartes aura), Gaviotas dominicanas y perros domésticos fueron también identificadas. Los Jotes en ausencia de perros vagos tienden a ser los carroñeros dominantes en este tipo de gremio. Las madres de los cachorros de lobo marino común despliegan conductas agonísticas ante la aproximación de jotes quienes se alimentan de las placentas y cordones umbilicales expulsados durante el parto. Se registraron conductas de tipo depredadora de jotes sobre cachorros vivos de lobo marino común. Entre un 12% y 17% de los cachorros sufrieron ataques por jotes durante ambas temporadas. Los perros vagos compiten en forma ventajosa con jotes por carroña. Se postula que la redirección de una conducta carroñera mutualista a depredadora, en el jote de cabeza negra, estaría influenciada por estrés alimentario, bajo el efecto competitivo dominante con perros vagos por cadáveres de lobos marinos.

Cats milking seals!!!

Juan-Pablo Gallo-Reynoso, J.P. & C. L. Ortiz. 2010. Feral cats steal milk from northern Elephant Seals. THERYA, 1(3): 207-212

Feral cats abound at Isla de Guadalupe; they forage on birds, mice, and placental tissue as well as carcasses of northern elephant seals (Mirounga angustirostris), Guadalupe fur seal (Arctocephalus townsendi), California sea lions (Zalophus californianus) and stranded cetaceans such as Cuvier’s beaked whale (Ziphius cavirostris). We have found that feral cats are also drinking elephant seal’s milk, stealing it directly from the teats of nursing females. The amount of energy obtained this way might be significant for feral cats in the northern elephant seal rookeries on the island.

Dogs outcompete Indian foxes for human-derived food

Vanak, A. T., & Gompper, M. E. (2009). Dietary niche separation between sympatric free-ranging domestic dogs and Indian foxes in central India. Journal of Mammalogy, 90(5), 1058-1065.

The competitive dynamics between domestic and native carnivores are poorly studied. We examined competition for food between sympatric populations of free-ranging dogs (Canis familiaris) and Indian foxes (Vulpes bengalensis) through dietary analysis in a protected, dry grassland habitat in central India. We expected significant dietary overlap between dogs and foxes because of clear evidence of interference competition between dogs and foxes in this area. However, dogs subsisted largely on human-derived foods (HDFs) from direct feeding, and scavenging on garbage, crop residue, and livestock carcasses (83% relative occurrence [RO]). Wild-caught foods constituted only 11% RO of the diet of dogs. The majority of the diet of Indian foxes consisted of invertebrates (33% RO), rodents (20% RO), and fruits of Zizyphus (18.5% RO). Indian foxes did not consume HDF, nor did they scavenge from large-mammal carcasses, and included only a small portion of agricultural produce in their diet. The low contribution of HDF and agricultural food sources to the diet of Indian foxes was surprising because this species is a generalist omnivore. Dogs may be preventing foxes from accessing agricultural lands and human-associated foods by interference competition.

Related posts

Dogs in rural Zimbabwe: disease transmission and competition with scavengers

Butler, J. R. A., & Toit, J. T. (2002). Diet of free‐ranging domestic dogs (Canis familiaris) in rural Zimbabwe: implications for wild scavengers on the periphery of wildlife reserves. Animal Conservation, 5(1), 29-37.

Numbers of free-ranging dogs (Canis familiaris) have reached unprecedented levels in Zimbabwean communal lands (agropastoralist rural areas). This study examined the potential competitive interactions between dogs and wild scavengers on the boundary of Gokwe Communal Land (GCL) and the Sengwa Wildlife Research Area (SWRA) in 1995–96. Dietary studies showed that dogs were primarily scavengers of human waste and animal carcasses. Twelve experimental carcasses indicated that dogs were the most successful species in the vertebrate scavenger guild, consuming 60% of available biomass and finding 66.7% of carcasses. Dogs monopolized the supply of domestic animal carrion within GCL, but also consumed wild carrion up to 1 km within the SWRA, and were seen 3 km inside the reserve. Their principal competitors for carcasses were vultures, and to a lesser degree lions (Panthera leo), leopards (P. pardus) and spotted hyaenas (Crocuta crocuta). Dogs outcompete vultures on wildlife reserve boundaries owing to their high densities, nocturnal and diurnal activity, physical dominance and greater tolerance of human disturbance. With a population growth rate of 6.5% per annum the influence of dogs will intensify on the peripheries of reserves, exacerbating their existing threat to wild scavengers. This scenario is probably occurring in many other African countries.

Butler, J. R. A., Du Toit, J. T., & Bingham, J. (2004). Free-ranging domestic dogs (Canis familiaris) as predators and prey in rural Zimbabwe: threats of competition and disease to large wild carnivores. Biological Conservation, 115(3), 369-378.

Domestic dogs (Canis familiaris) arrived in Zimbabwe ca. 1000 years ago. Numbers of free-ranging dogs have reached unprecedented levels in communal lands (agro-pastoralist rural areas), and interact with large wild carnivores along boundaries with wildlife reserves as predators and prey. This study examined a population of 236 dogs in a 33-km² section of Gokwe Communal Land (GCL) bordering the Sengwa Wildlife Research Area (SWRA) in north-western Zimbabwe in 1995–1996. Dogs were found up to 6 km within the SWRA, and were the most common carnivore on the GCL–SWRA boundary. Observations of 16 radio-collared dogs showed that they were inefficient predators. Only 20 kills were recorded amongst the remaining dog population, of which three were wild ungulates. Dogs were unsuccessful predators due to their small group size (mean 1.7) and body mass (mean 14.7 kg), and the abundance of alternative food. It is therefore unlikely that they compete with large carnivores for wild prey. However, leopards (Panthera pardus), lions (P. leo) and spotted hyaenas (Crocuta crocuta) preyed on dogs in GCL, removing ⩾6% of the dog population in 1993. Such predation provides ideal circumstances for disease transmission. Canid disease was prevalent in the study area; including rabies and probably distemper. The risk of infection is greatest during the dry season (May–October), when peaks in rates of disease, carnivore incursions into GCL, and predation on dogs coincided. The role of jackals (Canis adustus and Canis mesomelas) and spotted hyaena predation of dogs is discussed in relation to disease epidemics within wildlife reserves. With a dog population growth rate of 6.5% per annum, and the prevalence of canid diseases, the conservation threat posed by dogs is escalating on communal land–wildlife reserve boundaries in Zimbabwe. Measures to control dog numbers and improve vaccination coverage of dogs are discussed.

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.

More on Macquarie island cats

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.

Dogs as scavengers in India

http://www.indiawilds.com/diary/indiawilds-newsletter-vol-5-issue-ii/

A lot of people as well as animal welfare activists feed street dogs in various parts of our country. Whereas, animal welfare is good, one ought to understand the consequences of each of our actions.

Apart from the food given by people, due to our wasteful nature and the improper garbage disposal, a lot of street dogs find food. They outcompete our traditional scavengers like vultures and jackals. In the earlier days any dead animal used to be cleaned up by vultures, jackals and hyenas. Today with vultures impacted by diclofenac, during the day time it is the dogs who clean up the carcass. In the night, large wildboars get the first share, then the wildboar piglets followed by feral dogs and only after that the jackals get any chance to have food.

To stop the feral dog population from growing:

1) don't waste food

2) don't dump garbage

3) don't feed street dogs/feral dogs

Intraguild interactions between dogs and wild carnivores

Vanak, A.T. 2008. Intraguild interactions between native and domestic carnivores in Central India. PhD. University of Missoury

I determined the various factors affecting the resource selection and spatial ecology of the Indian fox Vulpes bengalensis, a small canid endemic to the Indian subcontinent. Despite being widespread throughout India, and commonly occurring in many dry grassland habitats, little is known about the ecology of this species. I investigated habitat selection by the Indian fox in a grassland region in central India that represents a mix of natural and human-dominated habitats to discern if and how foxes respond to human encroachment on native habitats. I collected home range and habitat selection data on 32 radio-collared Indian foxes in the Great Indian Bustard Wildlife Sanctuary, Nannaj, Maharashtra over a one year period. Adult Indian fox 95% kernel density home-range sizes varied between sexes and among seasons. Males had consistently larger home-ranges than females across all seasons but there was no interseasonal variation. Females had smaller home-range sizes during the cool-dry season which is also the denning period, than during any other season. Compositional analysis of Indian fox selection of home-ranges at the landscape level showed heavy influence of the presence of grasslands, plantations and fallow land. Indian foxes avoided humanmodified habitat such as agricultural land and human settlements. The presence of grasslands was also the dominant predictor of Indian fox habitat selection across seasons within the home-range as determined by AIC ranked discrete-choice models. The results indicate that Indian foxes select for natural grasslands and avoid human-modified habitat.
The distribution, abundance and resource selection patterns of meso-carnivores such as the Indian fox are also heavily influenced by the effects of top-down intraguild competition with sympatric larger carnivores. Competitive dynamics among carnivores are asymmetric and interference competition and the associated occurrence of intraguild predation are unidirectional, with larger carnivores negatively influencing smaller carnivores. Competition can affect the subordinate competitor in several ways: by limiting spatial distributions resulting in scattered interspecies territories, constraining habitat selection, reducing prey encounter rates and food intake, or requiring increased hunting effort.
In my study area, the domestic dog Canis familiaris, is the most common midsized carnivore. As the world’s most common carnivore, dogs are known to interact with wildlife as predators, prey, competitors, and disease reservoirs or vectors. Despite these varied roles in the community, the interaction of dogs with sympatric carnivores is not well understood. Dogs have the potential to be exploitative, interference and apparent competitors with sympatric carnivores.
I examined competition for food between dogs and the Indian fox through dietary analysis. Dogs subsisted largely on human derived material from direct feeding, and scavenging on garbage, crop residue and livestock carcasses (83% relative occurrence).

Wild caught foods constituted only 11% relative occurrence of dog diet. Indian foxes are omnivorous and included a wide variety of food types in their diet. The majority of  Indian fox diet consisted of invertebrates (33% relative occurrence), rodents (20% relative occurrence) and fruits of Zizyphus mauritiana (18.5% relative occurrence). Indian foxes did not include any human derived material, nor did they scavenge from large mammal carcasses, and included only a small portion of agricultural produce in their diet. The diet of free-ranging dogs is typical of dogs from other parts of the world. However, the low contribution of human-derived food sources to the diet of Indian foxes was surprising since the species is a generalist carnivore. Although there was limited dietary overlap between dogs and foxes in this study, dogs may actually be preventing foxes from accessing agricultural lands and human associated foods by interference competition.

Dogs have the potential to be effective interference competitors, especially with medium and small-sized carnivores, and may fulfill the role of a mid-sized canid, especially in areas where the native large carnivore community is depauperate. I experimentally examined the behavioral responses of the Indian fox to the presence of dogs and dog odors. Since resource competition between dogs and foxes is low, it is unclear whether foxes perceive dogs as interference competitors. To test this I exposed foxes to neutral, live dog, and animal odor cues at food trays and recorded the amount of food eaten, time spent at food trays, and vigilance and non-vigilance behaviors. When dogs were visible, foxes continued to visit the food trays, but reduced the amount of time spent (by 83%) and food eaten (by 70%) at those trays. Foxes were 10 times more vigilant during dog trials than during neutral and odor trials and also exhibited lower levels of non-vigilance behavior (resting, playing) when dogs were visible. In contrast, dog odors did not affect fox foraging and activity. These results show that vigilance/foraging tradeoffs due to interference competition can occur between native and domestic carnivores, despite low dietary overlap.

To avoid the effects of interference competition and intraguild predation, subordinate competitors such as the Indian fox can alter space use patterns which may result in a reduction of foraging opportunities. To determine if interference competition between dogs and foxes influences the space use patterns of foxes at a landscape level, I conducted a radio-telemetry study of 32 Indian foxes and 25 free-ranging dogs in and around the Great Indian Bustard Wildlife Sanctuary in central India. Using a logistic regression analysis in an information theoretic framework, I determined the effects of landcover type, primary prey abundance (rodents) and dog presence on the landscape on the space use of foxes. As expected, Indian foxes showed low overlap with dogs based on the volume of intersection index. Top AIC ranked models showed a positive influence of grasslands and a negative influence of agricultural land and dog presence. Rodent abundance only had a weak positive effect. This suggests that fox space use is determined not only by habitat type, but also influenced by the presence of a mid-sized carnivore, the dog.

These results suggest that the competitive intraguild dynamics that are seen among wild carnivores can also occur between wild and domestic carnivores, despite a seeming lack of competition for food and other resources. The role of dogs as intraguild competitors of wild carnivores has thus far been under-recognized. Dogs are among the world’s most common carnivores and are heavily subsidized by humans. As a result, they can occur at high densities even in rural areas, where they tend to range freely into wild habitats. Therefore, dogs can pose threats to native carnivore communities, and extend the edge of anthropogenic disturbance well beyond the borders of human settlements.

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