The condition and age of Thomson's gazelles killed by cheetahs and wild dogs

The condition and age of Thomson's gazelles ( Gazella thomsoni ) killed by two species of predators were compared. The wild dog, a coursing predator, was predicted to take a greater proportion of young, old and sick animals than the cheetah, a stalker. As measured by the marrow fat content of limb bones, wild dogs captured more Thomson's gazelles in poor condition than cheetahs. This appeared to be a consequence of their preference for male gazelles, which were in worse condition than females. Cheetahs did not capture fewer young and old gazelles than wild dogs.     

Migration patterns of Thomson's gazelles and cheetahs on the Serengeti Plains

Monthly changes in abundance of Thomson's gazelles at 142 locations on the Serengeti Plains are presented over a 3½ year period. Numbers of gazelles on the eastern plains were strongly correlated with rainfall, whereas numbers in the central and western plains appeared to be related to other variables. Movements of female cheetahs and non-resident male cheetahs corresponded closely to the movements of Thomson's gazelles but those of resident male cheetahs remained relatively independent of the gazelle migration.     

Prey preferences of the cheetah (Acinonyx jubatus) (Felidae: Carnivora): morphological limitations or the need to capture rapidly consumable prey before kleptoparasites arrive?

As a charismatic carnivore that is vulnerable to extinction, many studies have been conducted on predation by the cheetah Acinonyx jubatus . Cheetah are generally considered to capture medium-sized prey; however, which species are actually preferred and why has yet to be addressed. We used data from 21 published and two unpublished studies from six countries throughout the distribution of the cheetah to determine which prey species were preferred and which were avoided using Jacobs' index. The mean Jacobs' index value for each prey species was used as the dependent variable in multiple regression, with prey abundance and prey body mass as predictive variables. Cheetah prefer to kill and actually kill the most available prey present at a site within a body mass range of 23–56 kg with a peak (mode) at 36 kg. Blesbok, impala, Thomson's and Grant's gazelles, and springbok are significantly preferred, whereas prey outside this range are generally avoided. The morphological adaptations of the cheetah appear to have evolved to capture medium-sized prey that can be subdued with minimal risk of injury. Coincidentally, these species can be consumed rapidly before kleptoparasites arrive. These results are discussed through the premise of optimality theory whereby decisions made by the predator maximize the net energetic benefits of foraging. Information is also presented that allows conservation managers to determine which prey species should be in adequate numbers at cheetah reintroduction sites to support a cheetah population. Conversely, these results will illustrate which potential prey species of local conservation concern should be monitored for impact from cheetahs as several species are likely to be preyed upon more frequently than others.     

Experimental transmission of gastro-intestinal nematodes between sheep (Ovis aries) and Thomson's gazelles (Gazella thomsonii).

Experimental cross-transmission of gastro-intestinal nematodes between Merino sheep (Ovis aries) and Thomson's gazelles (Gazella thomsonii) from similar but separate grazing habitats in Kenya was studied. Cross-transmission did occur with some species but the faecal egg counts of sheep were higher than the gazelles' following infection with larvae isolated from either sheep or gazelles. Of the 11 gastro-intestinal nematodes which became established in gazelles following infection with larvae cultured from nematodes in gazelles, only Haemonchus contortus, Trichostrongylus probolurus and Cooperia hungi were infective for sheep. Following infection with larvae of either sheep or gazelle origin, the H. contortus recovered from the sheep at necropsy were more numerous and had greater average weights, lengths and spicule lengths than those recovered from the gazelles. This would suggest that H. contortus is primarily a sheep parasite. It is concluded that Thomson's gazelles probably would not contribute significantly to the problem of haemonchosis in sheep in areas of shared grazing, unless efforts were being made to eradicate the parasite from sheep, in which case the gazelles would act as a continuing reservoir of infection.     

The decline of the Serengeti Thomson's gazelle population

Summary The population of Thomson's gazelles in the Serengeti National Park, Tanzania has declined by almost two thirds over a 13 year period. In the early 1970s, numbers stood at 0.66 million animals but had decreased to less than 0.25 million animals in 1985 as estimated by 5 different censuses using two different counting techniques. Predation, interspecific competition and disease are all factors that could have contributed to this decline, and at least one of these factors, predation, could now prevent the Thomson's gazelle population from increasing.     

Comparative behaviour of sand and mountain gazelles

Behavioural observations of both captive and free-ranging sand and mountain gazelles revealed differences in group size and composition, territory size and agonistic behaviour. Sand gazelles are seasonal breeders and form large herds (maximum = 56) during rut and post-rut as compared to mountain gazelles, which breed throughout the year in smaller groups (maximum = 5). As a result, mountain gazelle males maintain their territories year round, whereas sand gazelle rams show marked morphological changes and defend a territory only during the rut. Mountain gazelle males exhibited threat displays rather than engaging in actual combat more often than did sand gazelles. Although subject to the same environmental conditions, sand gazelles are seasonal breeders and the young are born in March-April, whereas mountain gazelles give birth throughout the year.     

Midden site selection in Dorcas gazelle: Larger is not always better

Dorcas gazelles are believed to use middens to mark their territories and transmit information. Given the commitment to maintaining a midden, it is believed that middens are not placed randomly. We examined how the habitat (tree height and maximum canopy) and anthropogenic disturbance (camel and human presence) influenced the selection of midden sites by Dorcas gazelles in South Sinai, Egypt. Our results showed that Dorcas gazelles did not place middens at larger trees, while favoring relatively smaller trees and shrubs where the anthropogenic disturbance and perceived hunting risk are less. Our results, in light of the previous findings, suggest that selection of midden sites is species context‐dependent behavior. In areas with less anthropogenic disturbance and hunting, Dorcas gazelles have been shown to select the largest trees of the same species as midden sites. In contract, in our study site with high anthropogenic disturbance and no protection from hunting, gazelles did not utilize the presumably optimum landmarks for midden sites. Our study showed that Dorcas gazelles instead utilized smaller trees and some shrubs that are less conspicuous and presumably less effective as advertisement sites, but safer.     

Do nomadic avian predators synchronize population fluctuations of small mammals? a field experiment

Three-to-five-year population oscillations of northern small rodents are usually synchronous over hundreds of square kilometers. This regional synchrony could be due to similarity in climatic factors, or due to nomadic predators reducing the patches of high prey density close to the average density of a larger area. We estimated avian predator and small rodent densities in 4–5 predator reduction and 4–5 control areas (c. 3 km² each) during 1989–1992 in western Finland. We studied whether nomadic avian predators concentrate at high prey density areas, and whether this decreases spatial variation in prey density. The yearly mean number of avian predator breeding territories was 0.2–1.0 in reduction areas and 3.0–8.2 in control areas. Hunting birds of prey concentrated in high prey density areas after their breeding season (August), but not necessarily during the breeding season (April to June), when they were constrained to hunt in vicinity of the nest. The experimental reduction of breeding avian predators increased variation in prey density among areas but not within areas. The difference in variation between raptor reduction and control areas was largest in the late breeding season of birds of prey, and decreased rapidly after the breeding season. These results appeared to support the hypothesis that the geographic synchrony of population cycles in small mammals may be driven by nomadic predators concentrating in high prey density areas. Predation and climatic factors apparently are complementary, rather than exclusive, factors in contributing to the synchrony.     

Effects of habitat use on food acquisition and food caching during a nonbreeding season in a winter-breeding,food-storing passerine

ABSTRACT

Capsule: Wintering male Bull-headed Shrikes Lanius buchepalus preferred vegetable fields with perch sites to search for and detect terrestrial prey, and males occupying territories with large areas of vegetable fields acquired more prey and cached more food.

Aims: To better understand effects of habitat use on food acquisition and food caching of the Bull-headed Shrike, we investigated relationships between habitat quality (measured through foraging-site selection and foraging success) and food caching during the non-breeding season.

Methods: We monitored 66 territorial male shrikes during the non-breeding season from 2014 to 2016, and collected data on foraging-site selection, foraging success, and food caching.

Results: Our field observations showed that male shrikes preferred to forage over vegetable fields and that males occupying territories incorporating large areas of that habitat were able to acquire more food items and store more food caches in their territories during the nonbreeding season.

Conclusion: We suggest that for male Bull-headed Shrikes, a winter-breeding food-storing passerine, the quality of habitat in the nonbreeding season has the potential to affect their subsequent fitness.     

Food-niche differentiation in sympatric Hen Circus cyaneus and Montagu's Harriers Circus pygargus

Hen Harriers Circus cyaneus and Montagu's Harriers Circus pygargus are medium-sized raptors that differ in size (Hen Harrier being slightly bigger than Montagu's Harrier) and breeding system (Montagu's Harriers are semi-colonial and Hen Harriers defend nesting–hunting territories). In contrast, the diets of the two species when in sympatry are very similar. We evaluated food-niche differentiation among these coexisting raptor species and how between-species differences in body size and social system influence interspecific relationships. We present data from a study conducted in 1997 and 1998 in northeastern Madrid province (central Spain). Diet of the two species largely overlapped (55–95%) during the breeding season, but Hen Harriers preyed more often on larger species. This segregation was observed both in the average size of the primary prey (lagomorphs) and in the alternative prey (birds for Hen Harriers vs. insects for Montagu's Harriers), and was particularly apparent late in the season. Accordingly, feeding frequency of Montagu's Harriers, but not of Hen Harriers, increased later in the season. Size differences between species in prey brought to the nest were apparent for both males and females. Foraging behaviour also differed, as Hen Harriers spent more time hunting close to the nest than did Montagu's Harriers. This implies that segregation in foraging areas may also exist. Observed niche partitioning may relax the potential for competition between these species.     

Prey availability affects territory size,but not territorial display behavior,in green anole lizards

The availability of food resources can affect the size and shape of territories, as well as the behaviors used to defend territories, in a variety of animal taxa. However, individuals within a population may respond differently to variation in food availability if the benefits of territoriality vary among those individuals. For example, benefits to territoriality may differ for animals of differing sizes, because larger individuals may require greater territory size to acquire required resources, or territorial behavior may differ between the sexes if males and females defend different resources in their territories. In this study, we tested whether arthropod abundance and biomass were associated with natural variation in territory size and defense in insectivorous green anole lizards, Anolis carolinensis. Our results showed that both male and female lizards had smaller territories in a habitat with greater prey biomass than lizards in habitats with less available prey, but the rates of aggressive behaviors used to defend territories did not differ among these habitats. Further, we did not find a relationship between body size and territory size, and the sexes did not differ in their relationships between food availability and territory size or behavioral defense. Together, these results suggest that differences in food availability influenced male and female territorial strategies similarly, and that territory size may be more strongly associated with variation in food resources than social display behavior. Thus, anole investment in the behavioral defense of a territory may not vary with territory quality.     

Intra- and Inter-seasonal Variation in the Socio-Spatial Behavior of Adult Male Collared Lizards, Crotaphytus collaris (Reptilia, Crotaphytidae)

When individuals maintain strong inter‐seasonal philopatry to the same territories, males may be able to re‐establish territory occupancy without intense intra‐sexual aggression, and instead spend more time courting females early in the reproductive season. Furthermore, when some males have prior experience defending the same territories, it may be necessary for young males to exhibit higher levels of aggression because they are establishing a territory for the first time. We tested these hypotheses by examining within‐season (1992 and 1997) temporal variation in the social behavior of adult male collared lizards of known age and prior territorial experience in a population where inter‐season philopatry to territories is high. Contrary to expectations, the frequency of aggression exhibited by males with and without prior territorial experience did not differ. The frequency of intra‐sexual aggression was higher in 1992 than in 1997, perhaps because male competitors were more abundant in 1992. Although there was an interactive effect of year, male display and patrol were low at the beginning of the reproductive season in Apr. and May, reached peaks during midseason in June, and then decreased as reproduction ended in July. The size of territories showed a similar pattern, with males defending larger areas in June. Our data support the philopatry hypothesis in that the establishment of territories occurred without high levels of aggression early in the season, perhaps because territory boundaries have been well defined by high rates of patrol and advertisement during the middle of the previous season. Inter‐sexual interactions were most frequent in June rather than at the beginning of the reproductive season. Adult females are producing their second clutches and yearling females are producing their first clutches in June. The high rate of inter‐sexual encounters in June supports the hypothesis that males allocate more time to courtship when females are receptive because there are more reproductively active females at this time. The temporal pattern of activities in adult Crotaphytus collaris appears to function as a compromise between competing intra‐ and inter‐sexual social demands on males, allowing males to maximize mating opportunities as well as maintain future access to productive territories.     

Gyr Falcons, ptarmigan and microtine rodents in northern Sweden

A Gyr Falcon Falco rusticolus population in Northern Sweden (66°N, 17°E) was monitored from 1996 to 2002 in relation to its predator–prey interactions with its main and alternative prey species. Ptarmigan species Lagopus spp., and especially Rock Ptarmigan L. mutus , were the Gyr Falcons' most important prey and constituted more than 90% of the prey biomass. A 21-fold difference in ptarmigan abundance was found across Falcon breeding territories. However, this great variation in prey availability corresponded to only about a 10% shift in Gyr Falcon diet across territories, suggesting that the Falcons were reluctant or unable to compensate for declining ptarmigan availability by using alternative prey categories. Gyr Falcons did not respond functionally to microtine rodent abundance. Their diets were unaffected by a peak in the microtine rodent population cycle when Norwegian Lemmings Lemmus lemmus occurred in high numbers in the study area. Gyr Falcons responded numerically to their prey in two ways. First, there was a reproductive response with a significant relationship between the number of chicks fledged and the number of ptarmigan in the breeding territories. Secondly, although the Gyr Falcons did not utilize microtines as prey, there was a relationship between the microtine rodent abundance and the number of pairs that attempted to breed each year. This could be a result of an indirect community interaction, assuming that other predators switched from ptarmigan to microtines as prey, which could have had a positive effect on the breeding performance of the Gyr Falcons. The Gyr Falcons acted as true specialist predators, and their narrow food niche probably reflected a general lack of suitable alternative prey in the study area.     

Habitat selection and feeding ecology of the cheetah (Acinonyx jubatus) in thicket vegetation: is the cheetah a savanna specialist?

Habitat selection and feeding ecology of a reintroduced population of cheetahs Acinonyx jubatus were studied in a 16 000 ha game reserve in the Eastern Cape Province (South Africa). Seventy per cent of the reserve is characterized by very dense thicket vegetation (valley bushveld) and the remainder is open and savanna-like. The results illustrated a strong effect of sex and group size on the behaviour of cheetahs. The coalition (three adult males) killed significantly larger animals (55% of kills weighed more than 65 kg) than single female cheetahs (less than 2% of kills weighed more than 65 kg). Female cheetahs showed temporal and spatial avoidance of lions by hunting at dawn and dusk and positioning their home ranges [95% utilization distribution (UDs)] significantly farther from the pride of lions than did the coalition. The coalition hunted earlier and later than female cheetahs, and 46% of their kills were made in darkness. In addition, their home range overlapped that of the lions and they showed neither temporal nor spatial avoidance of the lions. The rates of kleptoparasitism were lower and the kill retention times were longer than those reported elsewhere in Africa, and it is suggested that this is a consequence of the cover provided by the thicket vegetation and prey size. The home ranges (95% UDs) of female cheetahs incorporated more thicket vegetation than that of the coalition, indicating that the coalition is less susceptible to predation than single females. These data suggest that cheetahs possess greater behavioural flexibility than previously reported, that they can hunt successfully in thicket vegetation, sometimes in darkness, that they are not restricted to killing small to medium-sized prey, and that they may not be savanna specialists.     

Antibodies against equine herpesviruses and equine arteritis virus in Burchell's zebras (Equus burchelli ) from the Serengeti ecosystem

A total of 51 sera from a migratory population of Burchell's zebras (Equus burchelli) were collected in the Serengeti National Park (Tanzania) between 1999 and 2001 to assess levels of exposure to equine herpesvirus types 1, 2, 4, 9 (EHV-1, -2, -4, -9), EHV-1 zebra isolate T965, and equine arteritis virus (EAV). Using virus-specific neutralizing antibody tests, seroprevalence was high for EHV-9 (60% of 45), moderate for EAV (24% of 51), and lower for the EHV-1-related zebra isolate (17% of 41), EHV-1 (14% of 49), and EHV-4 (2% of 50). No evidence for exposure to EHV-2 was found (0% of 51). The high level of exposure to EHV-9 is interesting because evidence of infection with this virus has not been previously described in any wild equine population. Although the epidemiology of EHV-9 in Burchell's zebras is presently unknown, our results suggest that in East Africa, this species may be a natural host of EHV-9, a neuropathogenic virus that was only recently isolated from captive Thomson's gazelles (Gazella thomsoni) in Japan. There is currently no evidence that EHV-9 induced mortality in Burchell's zebras in the Serengeti, but because of the reported virulence of this virus for more susceptible species such as Thomson's gazelles, viral transmission from infected zebras to ungulates may result in mortality.     

Male Cheetah Social Organization and Territoriality

Patterns of territory ownership in male cheetahs inhabiting the Serengeti Plains are described, and factors affecting territorial behaviour are examined. Body size and age were factors influencing whether males became territorial, and single males usually had to join up with others in order to oust residents. Both size of male coalition and body size of its members were associated with length of tenure on territories. Limited data suggest that territory owners were probably no more likely to encounter females than were non-territorial males but there was a suggestion that they suffered lower survivorship costs than non-territorial males.     

Population density,resource patterning,and territoriality in the Everglades pygmy sunfish

The means by which pygmy sunfish compete for food are influenced by the density of the population and the dispersion of the prey as well as by the sex and dominance status of the individual. At all densities when the prey were predictably located in a central clump, males established territories. When prey were dispersed randomly in both the high and low density population, males abandoned territorial behaviour and, like females, swam freely about the aquaria. Only in the intermediate density populations did the males maintain territories and continue to defend resources. Development of a simple cost-benefit model shows that male territorial behaviour is governed to a large extent by economic considerations. Despite these overall patterns, differences in competitive strategies were observed within populations. Dominant individuals tended to possess territories nearest the central patch of prey, and use the most intense and physiologically exhausting displays. Only under the most stressful conditions did they acquire significantly more food than subordinates, and even then these benefits were not translated into increased growth, largely because dominant fish engaged in disproportionately more energy-consuming contests.     

Breeding season diet of the Goshawk Accipiter gentilis in Wales

Information on the diet of the Goshawk Accipiter gentilis during the breeding season was collected in Wales during 1991–1993. Diet consisted mainly of birds (87%) and mammals (13%). Forty-five prey species were collected, ten of which were important in numerical or biomass terms: Feral Pigeon Columba livia , Woodpigeon Columba palumbus , Crow/Rook Corvus coronet Corvus frugilegus , Magpie Pica pica , Jay Garrulus glandarius , Mistle Thrush Turdus viscivorus , Song Thrush Turdus philomelos , Blackbird Turdus merula , Grey Squirrel Sciurus carolinensis and Rabbit Oryctolagus cuniculus . Pigeon biomass was important throughout the breeding season and was more important in the diet of nesting Goshawks on higher ground (>250 m). On lower ground, corvids, mammals and pigeons were the main contributors to the Goshawk diet. Rabbits were more frequently taken at lower nesting territories, and thrushes occurred at all altitudes. Mammals, particularly Grey Squirrel, were found in higher numbers in the diet of Goshawks nesting in small woods (<1000 ha) compared with the diet of Goshawks nesting in two large forests ( c . 3500 ha and c . 6100 ha). Goshawks preyed upon juvenile Woodpigeons, corvids and thrushes, and switched from young thrushes to young corvids as the latter became available. Predation peaks on young birds corresponded with the presence of nestling Goshawks in late May to early July. Predation of juvenile prey led to a decrease in mean prey item mass (April-May, 437 g; July, 376 g). No evidence was found to suggest that sexual size dimorphism in Goshawks resulted in partitioning of prey captured during the breeding season. Differences found were probably due to local abundance and vulnerability of prey species rather than specific selection by the two sexes.     

The Behavioral Ecology of Libellula luctuosa (Burmeister) (Anisoptera: Libellulidae): I. Temporal Changes in the Population Density and the Effects on Male Territorial Behavior

A single population of a common pond dragonfly, Libellula luctuosa, was studied at a site where the density of males increased dramatically during the breeding season. Early in the summer one active male was found on each territory on the pond. Satellite males were only occasionally found on the territories. Later in the season the number of males per territory increased so that two or more males simultaneously defended on many of the territories, and several satellite males occupied each of the territories. The number and rate of female visitations per day did not change over the summer. These factors resulted in a change in the operational sex ratio with variations in male density. Male behavior was also altered with increasing population density. As male density increased, males were less likely to be seen perching on their territories and more likely to be seen performing aggressive acts such as chasing nearby territorial males and chasing intruders. At high male density, the duration of territorial behaviors was shorter than at low male density. Thus, the percent of a time budget spent in any one activity did not change despite the change in number of males present. Male activity in L. luctuosa is not strictly determined by the opportunity for aggression. Costs of aggression associated with territoriality are minimized by maintaining flexible territorial behaviors.     

Scent marking in a territorial African antelope: I. The maintenance of borders between male oribi

Scent marking is ubiquitous among the dwarf antelope and gazelles of Africa, but its function has been the subject of debate. This study examined preorbital gland scent marking in the oribi, Ourebia ourebi, a territorial African antelope. Several hypotheses for the function of scent marking by territorial antelope were tested with observational data. Of these, the hypotheses that scent marking is driven by intrasexual competition between neighbouring males, and that marks serve as an honest advertisement of a male's ability to defend his territory from rivals, were supported best. Thirty-three territorial male oribi on 23 territories marked most at borders shared with other territorial males, and territorial males marked more often at borders shared with multimale groups than at borders shared with a single male. This suggests that males perceived neighbouring male groups as a greater threat to territory ownership than neighbouring males that defended their territories without the aid of adult subordinates. Marking rate was unrelated to territory size or the number of females on adjacent territories, but males with many male neighbours marked at higher rates than those with fewer male neighbours. These results suggest that the presence of male neighbours has a greater effect on the scent marking behaviour of territorial antelope than has been considered previously. Copyright 1999 The Association for the Study of Animal Behaviour.