Ethiopian Wolves
The EWCP has been the leader and foremost supporter of research on Ethiopian wolves that has greatly contributed to understanding of the species’ behavioural ecology and conservation threats in the Bale Mountains and elsewhere in Ethiopia. The first detailed field studies of Ethiopian wolves began in 1988 in the Bale Mountains, and still continue here as well as other wolf ranges in Ethiopia. Initial research between 1988 and 1992 provided the first detailed data on the wolves’ diet, foraging behaviour, territoriality, social structure, mating behaviour and dispersal. Subsequent researched expanded to other aspects of the wolves' ecology, population genetics, population dynamics, reproductive physiology, disease prevalence and control.
Ethiopian wolves - Behavioural Ecology
The first detailed studies of Ethiopian wolves in the mid 1980s unveiled to the world the behavioural ecology of this fascinating yet rare species and, particularly, its complex mating system and social structure. This was then followed up by further studies by researchers in the Wildlife Conservation Research Unit at the University of Oxford which elaborated on the existing information about the Ethiopian wolf’s behavioural ecology. It was discovered very early on that, as result of delayed dispersal, Ethiopian wolves form discrete and cohesive social packs that communally share and defend an exclusive territory. A pack can be formed by 3 to 13 adults (of which 3-8 are related adult males, 1-3 adult females, 1-6 yearlings and 1-6 pups), but in less productivity areas wolves also live in pairs. The home ranges of neighbouring packs are largely discrete, forming a mosaic of packs occupying all available habitat, and stable in time, drifting only during major pack readjustment after the disappearance of a pack or significant demographic changes. Territory boundaries are regularly patrolled, usually at dawn and evening, and maintained by active scent-marking. Research has also shown that the Ethiopian wolf’s mating system is exceptionally interesting, with breeding restricted to the dominant female in each pack but high levels of female promiscuity. Like many cooperatively breeding carnivores, other pack members help to suckle, guard and provision the dominant female’s pups. The dominant female discourages mating attempts from all but the dominant male in her pack. In contrast, she is receptive to any visiting male from neighbouring packs. Behavioural observations revealed that up to 70% of matings by a breeding female involve males from outside her pack. Female promiscuity and extra-pack copulations (EPCs) was supported by genetic analyses of parentage of pups showed that multiple paternity occurred in 33% of litters and extra-pack paternity was attributed to 28% of all pups.
Despite their social nature, Ethiopian wolves are solitary hunters. The species occurs at highest densities in the short herbaceous communities of the Afroalpine ecosystem where they live as specialist rodent predators feeding almost exclusively on diurnal Muridae rodents. Rodent prey such as the endemic giant mole rat (Tachyoryctes macrocephalus) and grass rats (e.g. Arvicanthis blicki, Lophuromys melanonyx, and Otomys typus) reach staggering densities in the Afroalpine – roughly 25 to 30 kg/ha. This is assumed to account for the higher densities and smaller home ranges of Ethiopian wolves compared to other wolf-like canids.
Research on Ethiopian wolf behavioural ecology was initially conducted by Claudio Sillero-Zubiri and Dada Gottelli with subsequent field studies undertaken by Jorgelina Marino, Lucy Tallents, Deborah Randall, and Freya van Kesteren.
Ethiopian wolves - Spatial ecology, resource partitioning and reproductive success
Ethiopian wolves have developed refined specialization to prey upon the rich rodent fauna of the Afroalpine ecosystem. Research into the spatial ecology of wolves has investigated the ways in which wolves respond to their environment at various spatial scales of habitat patchiness and heterogeneity. The focus was primarily on rodents as the critical resource for wolves and interpreting ecological patterns in terms of wolf behaviour, life-history traits, social group composition and external forces (e.g. disease). The findings showed that the ecological conditions for sociality and enlargement of packs are constrained by local patterns of resource availability. In areas where prey density is low, packs are smaller (usually pairs) but territories are larger in order to capture similar amounts of rodent-rich habitat, while larger groups have smaller territories in more prey rich areas. The findings strongly suggest that the high aggregation of rodents in the Afroalpine and, thus, the group benefits of securing a resource rich area may underlie the evolution of sociality in this species. This avenue of research also showed that the reproductive success of wolves in the Bale Mountains is limited by the abundance of their rodent prey and recruitment of offspring is constrained by intra-specific socio-ecological factors as well as infectious disease outbreaks when they occur.
This research was conducted by Jorgelina Marino and Lucy Tallents towards their PhDs with the Wildlife Conservation Research Unit at University of Oxford.
Ethiopian wolves - Population dynamics
Long-term monitoring data collected by the EWCP also enabled research into the dynamics of Ethiopian wolf subpopulations in the Bale Mountains. The findings showed that, in the absence of disease, Ethiopian wolf numbers are relatively stable and resilient to current levels of livestock grazing and human disturbance. A stable environment with a reliable and abundant food source, combined with high adult survivorship, may facilitate the long-term persistence of these small, isolated populations. Disease outbreaks that caused severe mortality among Ethiopian wolves in the Bale Mountains also unveiled new insights into population growth and recovery. Wolf numbers in Bale dropped to less than half during rabies epizootics in the early 90s, and by 1997 densities were still very low. By 2000, however, wolves and packs in two well-studied local populations had recovered to pre-epidemic levels. Fourteen years of population monitoring allowed us to unveil the process underlying recovery, by comparing the demography and spatial distribution of wolf packs in two time periods: one of high population density in a saturated environment – before epizootics – and a subsequent period of low density and population recovery – after epizootics. This natural experiment revealed intrinsic mechanism of population regulation, mediated by territoriality, delayed dispersal, and breeding structure. Ultimately, these combined effects mean that population recovery after disturbance is limited by the number of breeding units (or packs) since packs are the reproductive machinery of the population at large.
This research was conducted by Jorgelina Marino towards her PhD with the Wildlife Conservation Research Unit at University of Oxford.
Ethiopian wolves - Population genetics
The genetic consequences of small size and isolation on the persistence of Ethiopian wolf populations is an important consideration within the species’ overall conservation strategy, especially since the first genetic study on Ethiopian wolves in the Bale Mountains reported only 40% of the genetic variation found in other wolf-like canids. Previous and ongoing research in this area has targeted several inter-related aspects of the population’s genetic diversity and dynamics. Initial genetic research suggested that the evolutionary history of Ethiopian wolves is characterized by divergence from a Eurasian wolf-like ancestor and population expansions that coincided with the glacial periods, the most recent occurring roughly 70,000 to 10,000 years ago. Thus, genetic structuring of Ethiopian wolves today is the result of processes acting over the last 18,000 years, leading to their final retreat into modern mountain refuges. Research into the fine-scale genetic structure of the Bale Mountains population showed strong genetic structure at both the pack and subpopulation levels, which appears to be influenced by social structure, small effective population sizes, dispersal and localised bottlenecks caused by recurring outbreaks of infectious disease. Simulation modelling also showed that social structure helps to maintain genetic variation in this small, isolated population, but genetic diversity is adversely affected by recurring disease outbreaks. Given the suite of threats to the long-term persistence of Ethiopian wolf populations, this research suggested that overt genetic management is not a conservation priority for the population at the moment since genetic diversity is likely to be preserved as a by-product of core conservation strategies that ensure the demographic stability of Ethiopian wolf populations. One exception may be the threat that hybridization poses to the genetic integrity of the species, which deserves further examination.
Genetic research was initially conducted by Dada Gottelli at the Institute of Zoology-Zoological Society of London and later by Deborah Randall towards her PhD with the Wildlife Conservation Research Unit at the University of Oxford in collaboration with the University of California, Los Angeles.
Ethiopian wolves - Disease prevalence and control
The EWCP has documented at least two, possibly three, rabies outbreaks and one, possibly two canine distemper outbreaks in the Bale Mountains wolf population since the early 1990s. Thus, much research has been devoted to understanding the prevalence and dynamics of disease in Ethiopian wolf and reservoir populations and devising effective disease control measures to prevent or respond to disease outbreaks. Initial epidemiological research confirmed that spill-over from domestic dogs living in wolf habitat and surrounding areas is the source of pathogen transmission to Ethiopian wolves. The EWCP operates a continuous dog vaccination programmes in and around BMNP, but research suggests that as the dog population has grown, substantially more effort has been required to catch and vaccinate dogs and obtain the desired coverage to prevent epidemics. An emergency vaccination campaign in response to the 2003 rabies outbreak enabled researchers to test the efficacy of vaccinating Ethiopian wolves directly. They found that vaccinated animals did mount an initial immune response to inactivated rabies vaccine lasting about 6-12 months. Importantly, simulation modelling has shown that as the incidence of disease among domestic dogs increases, the frequency and severity of outbreaks among Ethiopian wolf populations are likely to increase and, thus, so will increase extinction risk. Modelling also showed that targeted low-coverage can be effective in curtailing disease outbreaks and enhance the long-term persistence of Ethiopian wolf populations. Research and field trials are currently underway to assess the efficacy and feasibility of oral vaccines as these may reduce the time and resources necessary to achieve desired vaccination coverage in dogs and Ethiopian wolves.
This research has been led by Karen Laurenson (University of Edinburgh) in collaboration with the Ethiopian Wolf Conservation Programme, the Bale Mountains National Park, the Ethiopian Wildlife Conservation Authority (formerly Ethiopian Wildlife Conservation Organisation), University of Glasgow, the Center for Disease Control and Prevention (USA), Onderstepport Veterinary Institute (RSA), the Central Veterinary Laboratory (UK), the Veterinary Laboratories Agency (UK), University of California-Davis. Dan Haydon (University of Glasgow) had led the disease modelling work and Darryn Knobel (University of Edinburgh) led the Ethiopian wolf vaccination campaign for EWCP in 2003-2004 and is currently undertaking the oral vaccination field trials. Funding has been provided by the Born Free Foundation, Frankfurt Zoological Society, the Wellcome Trust, the Morris Animal Foundation, the Peoples’ Trust for Endangered Species, the African Wildlife Foundation and Conservation International.
Ethiopian wolves - Reproductive physiology
Research is also being undertaken to understand the reproductive physiology of Ethiopian wolves. This includes characterizing females' hormone levels associated with oestrus, conception, pregnancy, birth and lactation. The research will also investigate the hormonal underpinnings of communal breeding in the species. Ethiopian wolves are communal breeders, and only the dominant pair in a pack breeds, although the dominant female may mate with males from other packs. This breeding system requires reproductive suppression of the subordinate females in a pack and a deeper understanding of the wolves’ reproductive physiology will shed light on how this is achieved. This may involve behavioural restrictions such as aggression, or physiological restrictions such as hormonal suppression. Because active handling of wolves is impractical and undesirable, faecal samples are being collected from focal individuals and evaluated in the lab to determine the hormonal information required.
This research is being conducted by Freya van Kesteren towards her PhD with the Wildlife Conservation Research Unit at University of Oxford.