Cat predation quantified with cams

Loyd, K. A. T., Hernandez, S. M., Carroll, J. P., Abernathy, K. J., & Marshall, G. J. (2013). Quantifying free-roaming domestic cat predation using animal-borne video cameras. Biological Conservation, 160, 183-189.

Domestic cats (Felis catus) are efficient and abundant non-native predators. Predation by domestic cats remains a topic of considerable social and scientific debate and warrants attention using improved methods. Predation is likely a function of cat behavior, opportunity to hunt, and local habitat. Previous predation studies relied on homeowner reports of wildlife captures from prey returns to the household and other indirect means. We investigated hunting of wildlife by owned, free-roaming cats in a suburban area of the southeastern USA. Specific research goals included: (1) quantifying the frequency of cat interactions with native wildlife, (2) identifying common prey species of suburban cats, and (3) examining predictors of outdoor behavior. We monitored 55 cats during a 1-year period (November 2010–October 2011) using KittyCam video cameras. Participating cats wore a video camera for 7–10 total days and all outdoor activity was recorded for analysis. We collected an average of 38 h of footage from each project cat. Forty-four percent of free-roaming cats hunted wildlife, of which reptiles, mammals, and invertebrates constituted the majority of prey. Successful hunting cats captured an average of 2.4 prey items during 7 days of roaming, with Carolina anoles (Anolis carolinensis) being the most common prey species. Most wildlife captures (85%) occurred during the warm season (March–November in the southern USA). Twenty-three percent of cat prey items were returned to households; 49% of items were left at the site of capture, and 28% were consumed. Our results suggest that previous studies of pet cat predation on wildlife using owner surveys significantly underestimated capture rates of hunting cats.

Highlights:
► We examined predatory behaviors of 55 owned, free-roaming domestic cats.

► We used animal-borne video cameras in suburban Athens, Georgia, USA. 

► Thirty percent of our sample captured wildlife. 

► Native reptiles, mammals, and invertebrates constituted the majority of prey. 

► Twenty-three percent of prey were returned to households.

Wolf-dog hybridisation in Italy

Verardi, A., Lucchini, V., & Randi, E. (2006). Detecting introgressive hybridization between free‐ranging domestic dogs and wild wolves (Canis lupus) by admixture linkage disequilibrium analysis. Molecular Ecology, 15(10), 2845-2855.

Occasional crossbreeding between free-ranging domestic dogs and wild wolves (Canis lupus) has been detected in some European countries by mitochondrial DNA sequencing and genotyping unlinked microsatellite loci. Maternal and unlinked genomic markers, however, might underestimate the extent of introgressive hybridization, and their impacts on the preservation of wild wolf gene pools. In this study, we genotyped 220 presumed Italian wolves, 85 dogs and 7 known hybrids at 16 microsatellites belonging to four different linkage groups (plus four unlinked microsatellites). Population clustering and individual assignments were performed using a Bayesian procedure implemented in structure 2.1, which models the gametic disequilibrium arising between linked loci during admixtures, aiming to trace hybridization events further back in time and infer the population of origin of chromosomal blocks. Results indicate that (i) linkage disequilibrium was higher in wolves than in dogs; (ii) 11 out of 220 wolves (5.0%) were likely admixed, a proportion that is significantly higher than one admixed genotype in 107 wolves found previously in a study using unlinked markers; (iii) posterior maximum-likelihood estimates of the recombination parameter r revealed that introgression in Italian wolves is not recent, but could have continued for the last 70 (± 20) generations, corresponding to approximately 140–210 years. Bayesian clustering showed that, despite some admixture, wolf and dog gene pools remain sharply distinct (the average proportions of membership to wolf and dog clusters were Qw = 0.95 and Qd = 0.98, respectively), suggesting that hybridization was not frequent, and that introgression in nature is counteracted by behavioural or selective constraints.


Read more about canine hybidisation and gene introgression

Dog-wolf hybrids in Iberia

GODINHO, R., LLANEZA, L., BLANCO, J. C., LOPES, S., ÁLVARES, F., GARCÍA, E. J., PALACIOS,V. CORTÉS, Y., TALEGÓN, J. & FERRAND, N. (2011). Genetic evidence for multiple events of hybridization between wolves and domestic dogs in the Iberian Peninsula.Molecular Ecology, 20(24), 5154-5166.

Hybridization between wild species and their domestic counterparts may represent a major threat to natural populations. However, high genetic similarity between the hybridizing taxa makes the detection of hybrids a difficult task and may hinder attempts to assess the impact of hybridization in conservation biology. In this work, we used a combination of 42 autosomal microsatellites together with Y-chromosome microsatellite-defined haplotypes and mtDNA sequences to investigate the occurrence and dynamics of wolf–dog hybridization in the Iberian Peninsula. To do this, we applied a variety of Bayesian analyses and a parallel set of simulation studies to evaluate (i) the differences between Iberian wolves and dogs, (ii) the frequency and geographical distribution of hybridization and (iii) the directionality of hybridization. First, we show that Iberian wolves and dogs form two well-differentiated genetic entities, suggesting that introgressive hybridization is not a widespread phenomenon shaping both gene pools. Second, we found evidence for the existence of hybridization that is apparently restricted to more peripheral and recently expanded wolf populations. Third, we describe compelling evidence suggesting that the dynamics of hybridization in wolf populations is mediated by crosses between male dogs and female wolves. More importantly, the observation of a population showing the occurrence of a continuum of hybrid classes forming mixed packs may indicate that we have underestimated hybridization. If future studies confirm this pattern, then an intriguing avenue of research is to investigate how introgression from free-ranging domestic dogs is enabling wolf populations to adapt to the highly humanized habitats of southern Europe while still maintaining their genetic differentiation.

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Hybridisation between dogs and wolves in Latvia

Andersone, Ž., Lucchini, V., & Ozoliņš, J. (2002). Hybridisation between wolves and dogs in Latvia as documented using mitochondrial and microsatellite DNA markers. Mammalian Biology-Zeitschrift für Säugetierkunde, 67(2), 79-90.

Crossbreeding between wolves and dogs in the wild has been sometimes reported, but always poorly documented in scientific literature. However, documenting frequency of hybridisation and introgression is important for conservation of wild living wolf populations and for the management of free ranging dogs. Here we report the results of molecular genetic analyses of 31 wolf samples collected in Latvia from 1997 to 1999, including six pups originated from a litter found in northern Latvia in March 1999, and six wolves showing morphological traits that suggested hybrid origin. Nucleotide sequencing of the hypervariable part of the mtDNA control-region and genotyping of 16 microsatellite loci suggested that both pups and the morphologically anomalous wolves might originate from crossbreeding with dogs. Causes of wolf-dog crossbreeding, as well as possible management effort to avoid further hybridisation in the wild, are discussed.

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Hybridization between wolves and dogs

Vila, C., & Wayne, R. K. (1999). Hybridization between wolves and dogs.Conservation Biology, 13(1), 195-198.

Concern has been expressed that European populations of gray wolves (Canis lupus) have extensively hybridized with domestic dogs (C. familiaris). We reviewed and analyzed surveys of mitochondrial and biparentally inherited genetic markers in dogs and wild populations of wolf-like canids. Although dog-wolf hybrids have been observed in the wild, significant introgression of dog markers into wild wolf populations has not yet occurred. Our investigation suggests that hybridization may not be an important conservation concern even in small, endangered wolf populations near human settlements. The behavioral and physiological differences between domestic dogs and gray wolves may be sufficiently great such that mating is unlikely and hybrid offspring rarely survive to reproduce in the wild.


En algunas ocasiones se ha sugerido que las poblaciones europeas de lobos (Canis lupus) pueden estar profundamente hibridadas con perros domésticos (C. familiaris). Revisamos y analizamos estudios que utilizan marcadores genéticos mitocondriales y de herencia biparental en perros y poblaciones silvestres de cánidos del grupo del lobo. Aunque existen observaciones de híbridos entre perros y lobos en condiciones naturales, nunca se ha observado una significativa introducción de marcadores genéticos de perros en las poblaciones de lobos. Nuestra revisión sugiere que la hibridación puede no ser un problema importante ni tan sólo para la conservación de poblaciones de lobos pequeñas y amenazadas, cerca de asentamientos humanos. Las diferencias fisiológicas y de comportamiento entre perros y lobos pueden ser suficientemente grandes como para que su apareamiento sea improbable y los híbridos tengan escasas posibilidades de sobrevivir y reproducirse en libertad.

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Oryx Editorial on cat predation in urban areas

van Heezik, Y. (2010). Pussyfooting around the issue of cat predation in urban areas. Oryx, 44(2), 153.

In an earlier editorial Adams (2007) argued for the integration of social science and conservation, despite differences in language and terminology and in traditions of enquiry and methodologies. He emphasized that conservation biologists need to think in an interdisciplinary way to make progress. Nowhere is this more evident than in the fledgling discipline of urban ecology...

Identification of wolf-dog hybrids

Vilà, C., C. Walker, A.-K. Sundqvist, Ø. Flagstad, Z. Andersone, A. Casulli, I. Kojola, H. Valdmann, J. Halverson, & H. Ellegren. 2003. Combined use of maternal, paternal and bi-parental genetic markers for the identification of wolf–dog hybrids. Heredity 90 (1): 17-24.

The identification of hybrids is often a subject of primary concern for the development of conservation and management strategies, but can be difficult when the hybridizing species are closely related and do not possess diagnostic genetic markers. However, the combined use of mitochondrial DNA (mtDNA), autosomal and Y chromosome genetic markers may allow the identification of hybrids and of the direction of hybridization. We used these three types of markers to genetically characterize one possible wolf–dog hybrid in the endangered Scandinavian wolf population. We first characterized the variability of mtDNA and Y chromosome markers in Scandinavian wolves as well as in neighboring wolf populations and in dogs. While the mtDNA data suggested that the target sample could correspond to a wolf, its Y chromosome type had not been observed before in Scandinavian wolves. We compared the genotype of the target sample at 18 autosomal microsatellite markers with those expected in pure specimens and in hybrids using assignment tests. The combined results led to the conclusion that the animal was a hybrid between a Scandinavian female wolf and a male dog. This finding confirms that inter-specific hybridization between wolves and dogs can occur in natural wolf populations. A possible correlation between hybridization and wolf population density and disturbance deserves further research.

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Diet of cats and impact on seabirds at Juan de Nova Island

Peck, D. R., Faulquier, L., Pinet, P., Jaquemet, S., & Le Corre, M. (2008). Feral cat diet and impact on sooty terns at Juan de Nova Island, Mozambique Channel. Animal Conservation, 11(1), 65-74.
Feral cat Felis catus predation on seabirds has been well documented; however, details regarding shifts in feral cat diet in relation to seabird availability, seabird predation rate and impact on seabird population dynamics are scarce. Here, we present data documenting a seasonal shift in feral cat diet at Juan de Nova Island, Mozambique Channel. We also quantify sooty tern Sterna fuscata predation by feral cats and examine the impact on sooty terns over both the short term (by removing individual cats from sub-colonies) and over the longer term by highlighting their influence on population growth rate (l) using a deterministic matrix model. Cat diet shifted dramatically from insects, rats and mice outside the tern breeding season to primarily terns when terns were breeding. The predation rate of sooty terns at Juan de Nova was estimated at 5.94 terns/cat /day , with a proportion of these (22%) being killed without being consumed (‘surplus kills’). When only one cat was removed from each sub-colony, tern predation declined tenfold in the short term. From our matrix model, the annual growth rate for sooty terns was 1.01 in the absence of cat predation. It remained above one until a predation impact equivalent to approximately three times the estimated cat density (12.04 per km²  was incorporated. Our results demonstrate that cats preferentially predate and have an impact on breeding sooty terns at Juan de Nova, and that an increase in cat density could lead to negative effects on population growth, despite the large breeding tern population

More on stable isotopes to know feral cat diet on islands

Keitt, B. S., Wilcox, C., Tershy, B. R., Croll, D. A., & Donlan, C. J. (2002). The effect of feral cats on the population viability of black‐vented shearwaters (Puffinus opisthomelas) on Natividad Island, Mexico. Animal Conservation, 5(3), 217-223.

Insular breeding seabirds are likely to be particularly vulnerable to introduced mammalian predators because they often lack behavioural, morphological and life-history defenses against predation. We studied the life-history of the black-vented shearwater (Puffinus opisthomelas) on Natividad Island, Baja California Sur, Mexico, to examine its vulnerability to introduced feral cats. Using an allometric equation, we estimated that feral cats consumed 328 g of food day-1 to satisfy their nutritional requirements. We used stable isotope analysis of cat scat to estimate that 90% of the cats' diet was composed of shearwaters. Using data from our focal species and from the closely related manx shearwater (Puffinus puffinus), we created a demographic model to evaluate the effects of cat population size on the annual growth rate (λ) of the shearwater. The annual growth rate for black-vented shearwaters was estimated to be 1.006 in the absence of cat predation. With predation, we estimated that annual growth rate declined approximately 5% for every 20 cats in a population of 150,000 birds. Persistence times of bird colonies decreased both with an increase in the size of the feral cat population and with a decrease in the size of the initial bird population.

Hybridization between dog and Ethiopian wolf

Gottelli, D, Sillero-Zubiri, C, Applebaum G.D., Roy MS, Girman D.J., García-Moreno, J., Ostrander, E.A. & Wayne, R.K.. (1994) Molecular genetics of the most endangered canid - the Ethiopian wolf Canis simensis. Molecular Ecology 3: 301–312.

The world's most endangered canid is the Ethiopian wolf Canis simensis, which is found in six isolated areas of the Ethiopian highlands with a total population of no more than 500 individuals. Ethiopian wolf populations are declining due to habitat loss and extermination by humans. Moreover, in at least one population, Ethiopian wolves are sympatric with domestic dogs, which may hybridize with them, compete for food, and act as disease vectors. Using molecular techniques, we address four questions concerning Ethiopian wolves that have conservation implications. First, we determine the relationships of Ethiopian wolves to other wolf-like canids by phylogenetic analysis of 2001 base pairs of mitochondrial DNA (mtDNA) sequence. Our results suggest that the Ethiopian wolf is a distinct species more closely related to gray wolves and coyotes than to any African canid. The mtDNA sequence similarity with gray wolves implies that the Ethiopian wolf may hybridize with domestic dogs, a recent derivative of the gray wolf. We examine this possibility through mtDNA restriction fragment analysis and analysis of nine microsatellite loci in populations of Ethiopian wolves. The results imply that hybridization has occurred between female Ethiopian wolves and male domestic dogs in one population. Finally, we assess levels of variability within and between two Ethiopian wolf populations. Although these closely situated populations are not differentiated, the level of variability in both is low, suggesting long-term effective population sizes of less than a few hundred individuals. We recommend immediate captive breeding of Ethiopian wolves to protect their gene pool from dilution and further loss of genetic variability.

Dogs threat to endangered huemul

From http://www.patagonjournal.com

Photo Paulo Corti

Patagonia's endangered huemul has its share of predators. Pumas, foxes, and the occasional poacher are expected, but a new threat has become a hounding concern in Chile's Aysen region. 

Dogs belonging to residents living near Lake Cochrane are killing young fawns, and injuring and sometimes killing adult huemul.

The huemul is a rare creature in the Patagonian landscape. An Andean deer that bears a strong resemblance to North American deer, the huemul (pronounced weh-MOOL) tends to live in much smaller groups. They are also docile creatures, a characteristic that may have sealed their fate.
“You can almost reach out and touch them,” says Paulo Corti, an animal ecologist and veterinarian at Chile's Austral University in Valdivia. He’s been tracking huemul populations since 2003 and estimates there are fewer than 2,000 left, living in 12 fragmented populations along the Argentine and Chilean slices of Patagonia, most of which live in Chile.
Since the arrival of Europeans in the 1500s, the huemul population has been in slow decline. Once abundant from central Chile to Tierra del Fuego, hunting initially cut huemul numbers in half. Now, the patchy Patagonian forests they inhabit are continually being cleared for tree farms, agriculture and development.
Though he is currently working on five ongoing studies throughout Patagonia, Corti's priority is a group of huemul in the Lake Cochrane National Reserve in southern Chile. In the past four years, this population has gone from 45 individuals down to around 30. Though his team can’t say with certainty if this decline is purely cyclical, they are especially worried right now about threats from dogs.
“The dogs attacking the huemul in the Lake Cochrane region are all from the town of Cochrane,” says Corti. “They’re dogs with first and last names.”
The small town of Cochrane sits on the two-laned Carretera Austral, or Southern Highway, at the foot of the steep hills of Lake Cochrane National Reserve. Most of the 3,000 residents raise sheep and cattle or farm crops.
Any visitor to Chile will report seeing vast numbers of dogs on streets, sometimes traveling in large packs. But curbing the numbers of street dogs, or wild dogs, in Chile is a contentious issue. Corti says they are untouchable and getting people to responsibly control their own dogs is a difficult challenge. “It’s a very long-term change. What we need is immediate change.”
In late September, huemul experts from Argentina and Chile convened in Valdivia, Chile, to make a comprehensive list of threats to the huemul’s survival. They suggested various techniques to slow the huemul’s decline, such as restoring and protecting more habitat, and improving connectivity between protected areas. The meeting led to the development of a formal “Binational Plan of Action for the Conservation of the Southern Huemul.”
But educating dog owners about their pets is surely one of the chief protection strategies. Says Corti: “Almost all of the dogs entering the reserve [near Cochrane] have owners, but Chileans are irresponsible with their mascots. Obviously, the dogs are hungry because their owners don’t feed them and let them freely roam.”

TNR evaluation: demography, home range and potential zoonosis

Nutter, F. B. 2005. Evaluation of a trap-neuter-return management program for feral cat colonies: population dynamics, home ranges, and potentially zoonotic diseases. PhD dissertation, North Carolina State University. Raleigh, NC. 

Management of feral cats is controversial, and alternatives to lethal control methods are gaining popularity. To evaluate the effectiveness of sterilization programs, nine feral cat colonies were divided into groups of three, managed either by spaying females and castrating males, spaying females and vasectomizing males, or leaving all cats intact. Colonies were followed intensively for four years, and intermittently for three additional years. Most cats were trapped in fewer than ten trap nights each. Breeding females produced a mean of 1.4 litters/year and 3 kittens/litter. Kitten mortality was 75% by 6 months of age. Feral and pet domestic cats had similar baseline health status and prevalences of FIV, FeLV, Cryptosporidium, Giardia, and Toxocara cati, but feral cats had higher prevalences of Bartonalla henselae and Toxoplasma gondii. Castrated male and spayed female cats survived longer than intact male and female cats. Survival times of vasectomized males were equivalent to those of intact males. Control colonies decreased in size and remained stable in composition, while intact colonies increased in size and had high turnover. One neutered colony went extinct and several others had fewer than five cats at the end of the project. Home ranges of both intact and neutered cats were small, usually less than 1 ha. Vasectomized males had larger home ranges than either intact or castrated males, probably because they were searching for intact females. Community-level stakeholder meetings were successful in building consensus among groups, and a basic decision tree for feral cat management was developed. Computer simulation modeling using VORTEX software suggested that harvesting breeding colonies every one or two years at 50% to 100% can keep colonies small, but will not lead to long-term reductions in cat numbers. Models of neutered colonies suggested that 75% to 80% sterilization is necessary to cause population decrease and eventual extinction. The mean estimated time to extinction of 12.8 years fits well with ongoing observations of steady decline in sterilized colonies.

Controversy on cat's eradication on Macquarie Island: predator or pathogen's release?

Bergstrom D, Lucieer A, Kiefer K, Wasley J, Belbin L, Pedersen T & Chown S (2009). Indirect effects of invasive species removal devastate World Heritage Island. Journal of Applied Ecology, 46: 73-81

A feral cat roams among baby penguins on Macquarie Island.
Photo: Geoff Copson/ Tasmanian NPWS

1. Owing to the detrimental impacts of invasive alien species, their control is often a priority for conservation management. Whereas the potential for unforeseen consequences of management is recognized, their associated complexity and costs are less widely appreciated.

2. We demonstrate that theoretically plausible trophic cascades associated with invasive species removal not only take place in reality, but can also result in rapid and drastic landscape-wide changes to ecosystems.

3. Using a combination of population data from of an invasive herbivore, plot-scale vegetation analyses, and satellite imagery, we show how a management intervention to eradicate a mesopredator has inadvertently and rapidly precipitated landscape-wide change on sub-Antarctic Macquarie Island. This happened despite the eradication being positioned within an integrated pest management framework. Following eradication of cats Felis catus in 2001, rabbit Oryctolagus cuniculus numbers increased substantially although a control action was in place (Myxoma virus), resulting in island-wide ecosystem effects.

http://ingervandyke.com/conservation/

4. Synthesis and applications. Our results highlight an important lesson for conservation agencies working to eradicate invasive species globally; that is, risk assessment of management interventions must explicitly consider and plan for their indirect effects, or face substantial subsequent costs. On Macquarie Island, the cost of further conservation action will exceed AU$24 million.

Dowding, J. E., Murphy, E. C., Springer, K., Peacock, A. J., & Krebs, C. J. (2009). Cats, rabbits, Myxoma virus, and vegetation on Macquarie Island: a comment on Bergstrom et al.(2009). Journal of Applied Ecology, 46(5), 1129-1132.

1. Eradication of a single pest species from a multiply invaded island system may have unpredicted and detrimental impacts.Bergstrom et al. (2009) describe damage to vegetation following an increase in the number of rabbits on Macquarie Island. They propose that the increase in rabbit numbers was caused solely by eradication of cats.

2. However, their modelling is flawed and their conclusion that cats were controlling rabbit numbers is unsupported. We suggest the increase was because of some combination of four factors: reduced releases of Myxoma virus, abundant food after 20 years of vegetation recovery, release from cat predation and climate variability.

3. Recent high numbers of rabbits on Macquarie Island are not unprecedented; vegetation has been damaged in the past but has recovered. Rabbit numbers appear to be in decline again in the absence of both cats and Myxoma releases, suggesting that other factors can contribute to regulation of rabbit numbers in this system.

4. We do not agree with the implication that pest management could have been better integrated. Eradication techniques for rodents and rabbits on an island the size of Macquarie were unavailable when cat eradication was deemed necessary. The benefits to seabirds of cat eradication have been rapid. Our analysis further highlights the complexity of multiply invaded island ecosystems.

Bergstrom, D. M., Lucieer, A., Kiefer, K., Wasley, J., Belbin, L., Pedersen, T. K., & Chown, S. L. (2009). Management implications of the Macquarie Island trophic cascade revisited: a reply to Dowding et al.(2009). Journal of Applied Ecology, 46(5), 1133-1136.

1. The management of non-indigenous species is not without its complications. In Bergstrom et al.’s (2009) study, we demonstrated that feral cats Felis catus on sub-Antarctic Macquarie Island were exerting top-down control on the feral rabbit Oryctolagus cuniculus population, and that the eradication of the cats led to a substantial increase in rabbit numbers and an associated trophic cascade.

2. Dowding et al. (2009) claim our modelling was flawed for various reasons, but primarily that a reduction in the application of the rabbit control agent, Myxoma virus, coinciding with cat removal, was a major driver of rabbit population release.

3. We explore this proposition (as well as others) by examining rates of Myxoma viral release between 1991 and 2006 (with an attenuation factor for the years, 2003–2006) in association with presence/absence of cats against two estimates of rabbit population size. Myxoma viral release was a significant factor in the lower estimates of rabbit population, but the effect was small, and was not significant for higher rabbit population estimates. By contrast, the presence or absence of cats remained highly significant for both estimates.

4.Synthesis and applications. We re-affirm our position that top-down control of rabbit numbers by cats, prior to their eradication, was occurring on Macquarie Island. Nonetheless, we agree with Dowding et al. (2009) that systems with multiple invasive species represent complex situations that require careful scrutiny. Such scrutiny should occur in advance of, during, and following management interventions.

More on Macquarie island cats

Professional, ethical, and legal dilemmas of TNR

Barrows, P. L. 2004. Professional, ethical, and legal dilemmas of trap-neuter-release. Journal of the American Veterinary Medical Association 225:1365–1369.

Although some have portrayed the current feral and abandoned cat trap-neuter-release (TNR) controversy as pitting cat haters against cat lovers, this is not the case. Those opposing TNR and the proliferation of free-roaming cats consider domestic cats to be important and valuable companion animals to the pet-owning public and their families. What opponents of TNR object to are cats in the wrong places doing destructive and undesirable things ...

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Dog-wolf hybridization in Baltic countries

Hindrikson M, Männil P, Ozolins J, Krzywinski A & Saarma U (2012) Bucking the trend in Wolf-Dog hybridization: First evidence from Europe of hybridization between female dogs and male wolves. PLoS ONE 7(10): e46465. doi:10.1371/journal.pone.0046465

Studies on hybridization have proved critical for understanding key evolutionary processes such as speciation and adaptation. However, from the perspective of conservation, hybridization poses a concern, as it can threaten the integrity and fitness of many wild species, including canids. As a result of habitat fragmentation and extensive hunting pressure, gray wolf (Canis lupus) populations have declined dramatically in Europe and elsewhere during recent centuries. Small and fragmented populations have persisted, but often only in the presence of large numbers of dogs, which increase the potential for hybridization and introgression to deleteriously affect wolf populations. Here, we demonstrate hybridization between wolf and dog populations in Estonia and Latvia, and the role of both genders in the hybridization process, using combined analysis of maternal, paternal and biparental genetic markers.

Figure 8. First-generation (F1) wolf-dog hybrids from Wildlife Park Kadzidlowo, Poland: female wolf×male Polish Spaniel (left); female wolf×West Siberian Laika (right) (photos: A. Krzywinski).

Eight animals exhibiting unusual external characteristics for wolves - six from Estonia and two from Latvia - proved to be wolf-dog hybrids. However, one of the hybridization events was extraordinary. Previous field observations and genetic studies have indicated that mating between wolves and dogs is sexually asymmetrical, occurring predominantly between female wolves and male dogs. While this was also the case among the Estonian hybrids, our data revealed the existence of dog mitochondrial genomes in the Latvian hybrids and, together with Y chromosome and autosomal microsatellite data, thus provided the first evidence from Europe of mating between male wolves and female dogs. We discuss patterns of sexual asymmetry in wolf-dog hybridization.

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