Census and distribution of large carnivores in the Tsavo national parks,a critical east African wildlife corridor

Kenya's Tsavo National Parks are a critical conservation area and the only wilderness corridor through densely populated human-dominated landscapes stretching from the East African coast to Lake Victoria, separating extensive undeveloped grasslands south of the equator from the undeveloped semiarid bushlands to the north. At nearly 21,000 km², Tsavo is one of four lion strongholds in East Africa and part of Africa's most important populations of all other large African carnivores. To provide baseline data on the status of large carnivores, a track survey was undertaken in 2013. Lions and both hyaena species were widely distributed across both parks, while cheetahs and wild dogs were more patchily distributed. Spotted hyaenas were the most abundant, with an estimated population of 3,903 ± 514 (95% CI), followed by lion (706 ± 201), striped hyaena (679 ± 144), leopard (452 ± 98), cheetah (154 ± 74) and wild dog (111 ± 92). Tsavo's carnivores suffer from bushmeat poaching, illegal grazing and retaliatory killing, and increasing human numbers on its periphery. Given Tsavo's importance as a stronghold for lions and an ecological corridor, increased investment in effective protection is strongly recommended. Evaluating trends will require complementary techniques in light of intensive monitoring requirements.     

Key factors and related principles in the conservation of large African carnivores

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Spoor counts as indices of large carnivore populations: the relationship between spoor frequency, sampling effort and true density

1. Studies of large carnivore populations and, particularly, reliable estimates of population density are necessary for effective conservation management. However, these animals are difficult to study, and direct methods of assessing population size and density are often expensive and time-consuming.
2. Indirect sampling, by counting spoor, could provide repeatable and inexpensive measures of some population parameters. The relationship between true population density and indirect sampling results has seldom been described in large carnivore studies.
3. In northern Namibia the population densities of leopards, lions and wild dogs were measured through recognition of individuals and groups. Spoor counts were then conducted independently, to assess the relationship between true density and the distribution of spoor.
4. Sampling effort, both in terms of the number of roads and total road distance in a sample zone, and the intensity of sampling, had a marked effect on the accuracy and precision of spoor frequency calculations.
5. In a homogeneous habitat, leopard spoor were evenly spread along different roads and spoor frequency was independent of road length. Taking into account very low sample sizes, the spoor density of leopards, lions and wild dogs showed a strong linear correlation with true density. The slope of the regression for leopards was different to that of lions and wild dogs.     

Natural and anthropogenic drivers of cub recruitment in a large carnivore

Recruitment is a critical parameter governing population dynamics and influences population persistence. Understanding the drivers of recruitment is therefore important for conservation, especially for long‐lived mammals such as large carnivores, which have low reproductive rates, rendering them prone to extinction. Using cheetahs (Acinonyx jubatus) as a model species, I investigated the variation in cub recruitment in relation to habitat and the abundance of tourists and predators. Per litter, female cheetahs on average raised 1.71 ± 1.35 cubs to independence, but this varied depending on the presence of open habitat and the abundance of tourists, both of which had a negative effect on cub recruitment. More specifically, female cheetahs that were mostly found in open habitats on average raised 1.69 ± 0.14 cubs per litter to independence compared to 3.04 ± 0.26 cubs in denser habitat. Similarly, female cheetahs that were exposed to high tourist abundance on average raised 0.21 ± 0.72 cubs to independence compared to 2.32 ± 0.11 cubs in low tourism areas. Neither lion nor spotted hyaena abundance had an impact on the number of cubs that were recruited. Based on these findings, I recommend that the importance of a heterogeneous environment should be taken into consideration in habitat management, restoration efforts, and reintroduction programs. In addition, tourist quotas should be put in place in high visitation areas and strict wildlife viewing guidelines, such as number of vehicles, tourist behavior, time spent, and distance to a sighting, should be enforced. Cub recruitment is an important component of species persistence and incorporating these findings could aid conservation efforts for species that are increasingly under threat.     

The ecology of large carnivores in the highlands of northern Ethiopia

The degradation and fragmentation of the northern Ethiopian highlands has resulted in frequent encounters of large carnivores with humans and their livestock. We interviewed 500 randomly selected households to estimate economic impact of livestock predation by spotted hyaena (Crocuta crocuta), leopard (Panthera pardus) and jackal (Canis aureus aureus) in the highlands of northern Ethiopia. The annual mean economic loss per household was approximately U.S.$ 20.2, about 7% of the average annual income of households in the area. Households surveyed reported losses of a total of 3122 livestock to hyaena, leopard and jackal predation over the past 5 years. This loss equated to a total financial loss of U.S.$ 50,381 . Livestock predation incidents of spotted hyaena, leopard and jackal demonstrated that spotted hyaena had a preference for dog, donkey, goat and sheep; leopard for goat, dog and sheep; and jackal for goat and sheep. Livestock predation of spotted hyaena and leopard were mainly during the night. We conclude that assessing depredation problems is important to develop actions for management of either livestock practices or wildlife conservation.     

Preliminary estimates of the population density of the Sokoke scops owl Otus ireneae Ripley in the East Usambara lowlands, Tanzania

Preliminary population density estimates are presented for a recently discovered population of the Sokoke scops owl Otus ireneae in the lowlands of the East Usambara mountains, Tanzania. Calling birds were mapped at two sites totalling 6·3 km². Approximate densities were 3–4 territories/km² in Kwamgumi Forest Reserve and <1·5 territories/km² in Manga Forest Reserve, a much more heavily logged site. Densities in prime habitat in Arabuko‐Sokoke forest, Kenya, the only other locality for the species, exceed seven territories/km². The total population in the East Usambaras cannot be calculated, but it is probably markedly smaller than in Arabuko‐Sokoke. Suggestions for more precise surveys are made.     

Sighting frequency and food habits of the leopard tortoise, Geochelone pardalis, in northern Tanzania

Sighting frequency and food habits of the leopard tortoise (Geochelone pardalis) were studied in northern Tanzania from October 1993 to June 1996. Sighting frequency varied significantly between protected (0.22 mhr^?1) and unprotected sites (0.59 mhr^?1), and between Arusha (0.27 mhr^?1) and Serengeti sites (0.56 mhr^?1). The tortoise diet comprised mostly plants (97.8%) and rarely inorganic matter (2.2%). A total of 47 plant species from 21 families was eaten. Forbs made up 74.5% of the plant items and monocots the remainder. Succulents contributed 51.0% of the plant items eaten while grasses and legumes accounted for 16.8% and 13.5%, respectively. Some plant items were eaten more frequently than their occurrence in the habitats.     

Growth and carapacial colour variation of the leopard tortoise, Geochelone pardalis babcocki, in northern Tanzania

Observations were made of growth rate and variation in colour pattern of the leopard tortoise ( Geochelone pardalis babcocki ) in northern Tanzania between October 1993 and June 1996. Growth rate differed significantly between tortoises, with immature animals (6.9 ± 1.4 mm month⁻¹) and females (5.7 ± 1.3 mm month⁻¹) exhibiting higher rates of growth than adult animals (2.9 ± 0.8 mm month⁻¹) and males (3.2 ± 1.1 mm month⁻¹), respectively. The faster growth rate in immature animals suggested that growth rate declined with age. The difference in growth rates between the sexes was ascribed to sexual dimorphism, adult females being larger and therefore growing faster than males.
The carapacial colour pattern observed in the northern Tanzanian tortoises was generally similar to that described elsewhere in the species' range. The colour pattern varied between Arusha and Serengeti District tortoises. Animals at the Arusha sites tended to be sparsely coloured (55.6%) compared to the Serengeti tortoises, which had a buff colouration with radiating spots (89.3%).; The sparse colouration provides effective camouflage in the drier Arusha habitats, as does the buff colouration with black spots in the wetter, darker habitats in the Serengeti.     

Consequences of different forms of conservation for large mammals in Tanzania: preliminary analyses

We examined the effects of protection from human activities and effects of tourist hunting on densities of 21 large mammal species in Tanzania. Aerial censuses revealed that mammal biomass per km² was highest in National Parks. Densities of nine ungulate species were significantly higher in National Parks and Game Reserves than in areas that permitted settlement; these tended to be the larger species favoured by poachers. The presence of tourist hunters had little positive or negative impact on ungulate densities, even for sought-after trophy species; limited ground censuses confirmed these results. Our analyses suggest that prohibition of human activity, backed up by on-site enforcement, maintains ungulate populations at relatively high densities, and challenge the idea that enforcement is only effective when spending is high.     

Foraging costs,hunting success and its implications for African wild dog (Lycaon pictus) conservation inside and outside a protected area

When selecting a habitat, animals utilize habitat in which they yield the highest rate of energy. Differences in foraging costs and hunting success are therefore likely to affect habitat choice. In a previous study, we showed that African wild dog (Lycaon pictus) packs with territories inside Hwange National Park (HNP), over the course of several years, moved their territories into the buffer zone outside HNP, where reproductive success was higher but anthropogenic mortality exceeded natality. In this study, based on long‐term radio‐telemetry data from 22 African wild dog packs, we analysed whether differences in foraging costs and hunting success could have contributed to this territorial drift. Taking seasonality and pack size into account, we determined foraging costs (foraging distance and chase distance) and hunting success (successful or failed chase) inside and outside HNP. Although we observed no difference in foraging costs, hunting success was higher outside HNP, which is likely to have contributed to the territorial drift into the buffer zone outside the protected area. This study shows the importance of taking factors affecting hunting success into account in the conservation strategy of African wild dogs.     

Spotted hyaena Crocuta crocuta feeding ecology and selectivity of large herbivorous prey in the Namib desert

We have investigated the relationship between spotted hyaenas in the south Namib Desert and large herbivorous prey and have summarized an updated overview of predator‐prey relationships in this resource‐limited arid environment. Over the 52‐month study, we recorded the densities (#/km⁻², ±SE) of the four local large herbivorous prey species: gemsbok (1.229, ±0.50), springbok (1.352, ±0.48), ostrich (0.648, ±0.23), and greater kudu (0.343, ±0.00). A fecal analysis was performed on 146 collected spotted hyaena scats, and prey items were identified and hairs cross‐follicle analyzed to the species level. Spotted hyaena diet at the study area remained opportunistic with 240 identified prey items representing eight differing prey species being recorded, ranging from ostrich eggs to large ungulates. The Ivlev''s Electivity Index was used to determine which large herbivorous prey was most selected for. Although gemsbok had a higher representation of prey items in the sampled scats, all sampled large herbivorous prey species scored below 0 and are thus generally avoided in relation to their availability in the environment. If any prey preferences are expressed by spotted hyaena in the Namib, it can be presumed to be a nonsampled prey species. We therefore promote further detailed investigations into all other prey species present, and seasonal variations of prey densities and scat sampling, within the study environment.     

Lion density and population structure in the Selous Game Reserve: evaluation of hunting quotas and offtake

In 1992, tourist hunting in the Selous Game Reserve generated 1.28 million dollars for the Tanzanian government, of which 0·96 million dollars were returned to wildlife conservation. Lions ( Panthera leo ) are one of three critical species for tourist hunting, consistently generating 12%–13% of hunting revenue from 1988 to 1992. Because of their ecological and economic importance (and intrinsic value), it is important that lion quotas be set so that offtake is sustainable. The population density of lions in Selous ranges from 0·08 to 0·13 adults km⁻², comparable to unhunted ecosystems. The adult sex ratio (36–41% male) and the ratio of cubs to adults (29% cubs) are similar to those of unhunted populations. The ratio of lions to hyaenas is lower in heavily hunted areas (0·17 lions/hyena) than in unhunted areas (0·43 lions/hyena). Hunting levels between 1989 and 1994 took 2·7–4·3% of adult males annually, which is sustainable. The current quota is 10–16% of the adult male population, which exceeds natural mortality rates for male lions. To remain stable if the quota was filled, the population would have to compensate via increased fecundity, increased juvenile survival, or an altered sex‐ratio. Compensation occurs in Selous by producing (or raising) more male than female cubs (66–81% of juveniles are male). Only 28% of the Selous quota was filled in 1992. The percentage of quota filled (both in Selous and nationwide) has dropped since 1988 as quotas have increased. The current intensity of lion hunting in Selous is sustainable, but the quota cannot be filled sustainably.     

Patterns of livestock depredation and cost‐effectiveness of fortified livestock enclosures in northern Tanzania

Human–carnivore conflicts and retaliatory killings contribute to carnivore populations' declines around the world. Strategies to mitigate conflicts have been developed, but their efficacy is rarely assessed in a randomized case–control design. Further, the economic costs prevent the adoption and wide use of conflict mitigation strategies by pastoralists in rural Africa. We examined carnivore (African lion [Panthera leo], leopard [Panthera pardus], spotted hyena [Crocuta crocuta], jackal [Canis mesomelas], and cheetah [Acinonyx jubatus]) raids on fortified (n = 45, total 631 monthly visits) and unfortified (traditional, n = 45, total 521 monthly visits) livestock enclosures (“bomas”) in northern Tanzania. The study aimed to (a) assess the extent of retaliatory killings of major carnivore species due to livestock depredation, (b) describe the spatiotemporal characteristics of carnivore raids on livestock enclosures, (c) analyze whether spatial covariates influenced livestock depredation risk in livestock enclosures, and (d) examine the cost‐effectiveness of livestock enclosure fortification. Results suggest that (a) majority of boma raids by carnivores were caused by spotted hyenas (nearly 90% of all raids), but retaliatory killings mainly targeted lions, (b) carnivore raid attempts were rare at individual households (0.081 raid attempts/month in fortified enclosures and 0.102 raid attempts/month in unfortified enclosures), and (c) spotted hyena raid attempts increased in the wet season compared with the dry season, and owners of fortified bomas reported less hyena raid attempts than owners of unfortified bomas. Landscape and habitat variables tested, did not strongly drive the spatial patterns of spotted hyena raids in livestock bomas. Carnivore raids varied randomly both spatially (village to village) and temporally (year to year). The cost‐benefit analysis suggest that investing in boma fortification yielded positive net present values after two to three years. Thus, enclosure fortification is a cost‐effective strategy to promote coexistence of carnivores and humans.     

Effects of a hydropower plant on Coleopteran diversity and abundance in the Udzungwa Mountains, Tanzania

The effects of river flow diversion on biodiversity were assessed using Coleoptera as an indicator group in three habitats of the Kihansi Gorge (Udzungwa Mountains, Tanzania), before and after commissioning of a hydropower plant. Data collected using sweep netting and pitfall traps showed that the effect of diversion of the river flow was site-specific, affecting particularly the spray habitat. Rarefaction analysis of both sweep netting and pitfall samples indicated that the expected richness of Coleoptera declined significantly in all habitats after commissioning of the power plant. Sweep netting and pitfall samples showed that the highest Shannon–Wiener diversity index value before the diversion of the river flow was in the spray zone, but the index value decreased after diversion. Changes in the other two habitats were less prominent. Analysis of variance using diversity index values from five pitfall samples in each habitat type before and after commissioning indicated that there were no statistically significant differences in the diversity index between the two sampling periods or among the three habitat types. Renkonen's similarity index between habitats showed that pitfall samples had higher similarity (87%) than did samples from sweep netting (69%). It is suggested that for mitigation purposes, artificial spray systems, which have been installed in other wetlands of the Kihansi Gorge, also be installed to cover the whole Lower Wetland in which this study was undertaken. In order to maintain overall biodiversity in the Kihansi Gorge, it is suggested that the ecosystem conservation approach be prioritised.     

Small pack size imposes a trade-off between hunting and pup-guarding in the painted hunting dog Lycaon pictus

The painted hunting dog or African wild dog, Lycaon pictus,is one of the most endangered large carnivores in Africa, withextinction predicted within a few decades if their dramaticdecline is not stopped. It has recently been hypothesized thatbecause of their constraining need for helpers, group sizewas of major importance in obligate cooperative breeding species,and that the resulting likely existence of a threshold numberof adults could create an Allee effect, increasing the groupextinction risk. One example where the importance for a criticalnumber of adults may have major repercussions for painted huntingdogs concerns baby-sitting, or pup-guarding, a behavior typicalof obligate cooperative breeders. We propose that, as forgoingthis behavior is costly because pup guards have the potentialto decrease pup mortality, its use is costly too, especiallyin small packs, because helpers are strongly needed for theircooperative foraging (hunting, protecting the kill and bringingback food to the pups). We present a simple model showing howpup-guarding imposes a cost because it implies that less foodper hunt is brought back to more individuals at the den. Wecomplete these analyses with empirical tests of the effectof pack size on the probability of pup-guarding, from fielddata from the Hwange population in Zimbabwe. Our model, aswell as our 5 years of empirical data, both suggest a criticalthreshold at a size of about five individuals.     

Seasonal variation of tsetse fly species abundance and prevalence of trypanosomes in the Maasai Steppe,Tanzania

Tsetse flies, the vectors of trypanosomiasis, represent a threat to public health and economy in sub‐Saharan Africa. Despite these concerns, information on temporal and spatial dynamics of tsetse and trypanosomes remain limited and may be a reason that control strategies are less effective. The current study assessed the temporal variation of the relative abundance of tsetse fly species and trypanosome prevalence in relation to climate in the Maasai Steppe of Tanzania in 2014–2015. Tsetse flies were captured using odor‐baited Epsilon traps deployed in ten sites selected through random subsampling of the major vegetation types in the area. Fly species were identified morphologically and trypanosome species classified using PCR. The climate dataset was acquired from the African Flood and Drought Monitor repository. Three species of tsetse flies were identified: G. swynnertoni (70.8%), G. m. morsitans (23.4%), and G.pallidipes (5.8%). All species showed monthly changes in abundance with most of the flies collected in July. The relative abundance of G. m. morsitans and G. swynnertoni was negatively correlated with maximum and minimum temperature, respectively. Three trypanosome species were recorded: T. vivax (82.1%), T. brucei (8.93%), and T. congolense (3.57%). The peak of trypanosome infections in the flies was found in October and was three months after the tsetse abundance peak; prevalence was negatively correlated with tsetse abundance. A strong positive relationship was found between trypanosome prevalence and temperature. In conclusion, we find that trypanosome prevalence is dependent on fly availability, and temperature drives both tsetse fly relative abundance and trypanosome prevalence.     

Leopard abundance,distribution and food habits in the Mt. Rungwe–Kitulo landscape,Southern Tanzania

Between 2003 and 2010, 2178.5 km of transect was walked and 76 leopard scats counted in the Mt. Rungwe–Kitulo landscape. The number of scats per 10 km ranged between 0 and 0.83 in Mt Rungwe and between 0 and 1.41 in Kitulo. Leopards chiefly selected bamboo forest between 2500 and 2950 m asl. Some 126 interviews revealed that leopards were encountered more in the 1980s than latterly. Leopards used to attack livestock, but in the 1960s and 1970s, were heavily poisoned. We analysed 59 scats for undigested materials and compared them to a hair reference atlas. Some 135 different prey items were found, with an average of 2.3 items per scat. Some 14 samples were identified to species level and four to genus level. The average prey body weight was 5.9 kg. The diet was dominated by small mammals and rodent species up to 5.0 kg (59.57%) of biomass, followed by carnivores (29.14%), primate species (8.91%) and small rodents <1 kg (2.24%). The highest relative biomass consumed was prey classes of 1.1–5.0 kg (61.06%), followed by prey 5.1–50 kg (35.22%) and small rodents <1 kg (2.24%). The total absence of ungulate prey and conservation implications are discussed.     

Status,trends, and equilibrium abundance estimates of the translocated sea otter population in Washington State

Sea otters (Enhydra lutris kenyoni) historically occurred in Washington State, USA, until their local extinction in the early 1900s as a result of the maritime fur trade. Following their extirpation, 59 sea otters were translocated from Amchitka Island, Alaska, USA, to the coast of Washington, with 29 released at Point Grenville in 1969 and 30 released at La Push in 1970. The Washington Department of Fish and Wildlife has outlined 2 main objectives for sea otter recovery: a target population level and a target geographic distribution. Recovery criteria are based on estimates of population abundance, equilibrium abundance (K), and geographic distribution; therefore, estimates of these parameters have important management implications. We compiled available survey data for sea otters in Washington State since their translocation (1977–2019) and fit a Bayesian state-space model to estimate past and current abundance, and equilibrium abundance at multiple spatial scales. We then used forward projections of population dynamics to explore potential scenarios of range recolonization and as the basis of a sensitivity analysis to evaluate the relative influence of movement behavior, frontal wave speed, intrinsic growth, and equilibrium density on future population recovery potential. Our model improves upon previous analyses of sea otter population dynamics in Washington by partitioning and quantifying sources of estimation error to estimate population dynamics, by providing robust estimates of K, and by simulating long-term population growth and range expansion under a range of realistic parameter values. Our model resulted in predictions of population abundance that closely matched observed counts. At the range-wide scale, the population size in our model increased from an average of 21 independent sea otters (95% CI = 13–29) in 1977 to 2,336 independent sea otters (95% CI = 1,467–3,359) in 2019. The average estimated annual growth rate was 12.42% and varied at a sub-regional scale from 6.42–14.92%. The overall estimated mean K density of sea otters in Washington was 1.71 ± 0.90 (SD) independent sea otters/km² of habitat (1.96 ± 1.04 sea otters/km², including pups), and estimated densities within the current range correspond on average to 87% of mean sub-regional equilibrium values (range = 66–111%). The projected value of K for all of Washington was 5,287 independent sea otters (95% CI = 2,488–8,086) and 6,080 sea otters including pups (95% CI = 2,861–9,300), assuming a similar range of equilibrium densities in currently un-occupied habitats. Sensitivity analysis of simulations of sea otter population growth and range expansion suggested that mean K density estimates in currently occupied sub-regions had the largest impact on predicted future population growth (r² = 0.52), followed by the rate of southward range expansion (r² = 0.26) and the mean K density estimate of currently unoccupied sub-regions to the south of the current range (r² = 0.04). Our estimates of abundance and sensitivity analysis of simulations of future population abundance and geographic range help determine population status in relation to population recovery targets and identify the most influential parameters affecting future population growth and range expansion for sea otters in Washington State.     

Effects of a protection gradient on carnivore density and survival: an example with leopards in the Luangwa valley,Zambia

Human activities on the periphery of protected areas can limit carnivore populations, but measurements of the strength of such effects are limited, largely due to difficulties of obtaining precise data on population density and survival. We measured how density and survival rates of a previously unstudied leopard population varied across a gradient of protection and evaluated which anthropogenic activities accounted for observed patterns. Insights into this generalist's response to human encroachment are likely to identify limiting factors for other sympatric carnivore species. Motion‐sensitive cameras were deployed systematically in adjacent, similarly sized, and ecologically similar study areas inside and outside Zambia's South Luangwa National Park (SLNP) from 2012 to 2014. The sites differed primarily in the degree of human impacts: SLNP is strictly protected, but the adjacent area was subject to human encroachment and bushmeat poaching throughout the study, and trophy hunting of leopards prior to 2012. We used photographic capture histories with robust design capture–recapture models to estimate population size and sex‐specific survival rates for the two areas. Leopard density within SLNP was 67% greater than in the adjacent area, but annual survival rates and sex ratios did not detectably differ between the sites. Prior research indicated that wire‐snare occurrence was 5.2 times greater in the areas adjacent to the park. These results suggest that the low density of leopards on the periphery of SLNP is better explained by prey depletion, rather than by direct anthropogenic mortality. Long‐term spatial data from concurrent lion studies suggested that interspecific competition did not produce the observed patterns. Large carnivore populations are often limited by human activities, but science‐based management policies depend on methods to rigorously and quantitatively assess threats to populations of concern. Using noninvasive robust design capture–recapture methods, we systematically assessed leopard density and survival across a protection gradient and identified bushmeat poaching as the likely limiting factor. This approach is of broad value to evaluate the impacts of anthropogenic activities on carnivore populations that are distributed across gradients of protection.