Variation of group size among African buffalo herds in a forest‐savanna mosaic landscape

Taxonomy The name Bos caffer was attributed by Sparrman in 1779. Since then, 92 species names have been given to the African buffalo. Taxonomists initially thought that each buffalo form represented a distinct species. Brooke (1873, 1875), who established the first classification of the African buffalo, reduced the number to three. Later, Blancou (1935) described up to 12 subspecies of buffalo. Haltenorth (1963), Ansell (1972) and Grubb (1972) summarized the first classifications of Christy (1929), Schouteden (1945) and Blancou (1935, 1954), concluding that all forms should be considered as monospecific. Although there are considerable morphological variations in body size, fur colour, horn shape and size throughout the range of distribution, the African buffalo is currently considered as a single species by various authorities (IUCN 2013; Prins & Sinclair 2013), with a subdivision into four subspecies: Cape buffalo ( S. c. caffer ), forest buffalo ( S. c. nanus ), West African savanna buffalo ( S. c. brachyceros ), and Central African savanna buffalo ( S. c. aequinoctialis ). Additionally to those four subspecies, a mountain form( S. c. mathewsi ) was also described in East Africa and may be distinct (Kingdon 1982).

Forest buffalo (Syncerus caffer nanus) occur throughout the Congo Basin forest region of central Africa. Unlike for the well-studied Cape (or savanna) buffalo (Syncerus caffer caffer), few data exist for forest buffalo. I tracked 7 radiocollared adult female forest buffalo at Lopé National Park, Gabon, over a 2-year period (2002–2004) to examine home ranges, habitat selection, and diurnal activity patterns. Home ranges of female forest buffalo averaged 4.55 km2 in area (mean number of locations per animal = 205); the percent of home-range overlap between individual radiocollared buffalo was small. Home ranges remained the same size and in the same locations over both study years. Distance analysis of habitat use from radiotracking data was used to assess forest buffalo habitat selection at 2 spatial scales. At the landscape scale, buffalo selected savanna and marsh habitat over forest habitat within a 72-km2 study area. Thus, forest buffalo home ranges were savanna-dominated despite the greater amount of forest habitat available in the overall landscape. At the scale of the home range (2.30–7.64 km2), habitat selection within home ranges varied with season. Adult female forest buffalo preferred forest habitat between March and August but preferred marsh to forest between September and February. Forest buffalo dwell in forest habitat, feed in savannas, and wallow in marshes, utilizing all habitat types in the landscape. Although the subspecies is forest-dwelling, forest buffalo depend on open habitat adjacent to continuous forest.

We estimated sizes of over 90 social groups of Aphelocoma ultramarina in various regions of Mexico and recorded the presence or absence of Rattle calls. Group size over most of Mexico was similar to that in Arizona, not to that in Texas. We found that geographic variation in mean group size was not correlated with ontogeny of bill color. Group size correlated positively with body size. Rattles were found only in A. u. couchii but not in all populations. We hypothesize that natural selection may not be the only factor responsible for the patterns observed.

Understanding mechanisms that influence the grouping tendencies of large herbivores is necessary to predict the influence of environmental and human factors on threatened populations. Locations of 53 adult female pronghorn (Antilocapra americana) in Yellowstone National Park during June 1999–April 2005 indicated that mean and typical group sizes and the variation in group size decreased during fawning when females secluded themselves, but became larger and more dynamic during fawn rearing and the rut and winter. Mixed-effects models indicated a strong effect of time of year on mean group sizes, with some evidence that predators negatively affected group sizes during winter. Within-animal variability (0.64) was substantially higher than between-animal variability (0.02). Pronghorn density, snow water equivalent, and predation apparently influenced variations in group size. Multiple regressions indicated effects of pronghorn density and snow water equivalent on typical group size, the size of the g...

The time devoted to eating, vigilance (or scanning), walking and aggression was studied in one-minute focal animal samples as a function of sex, age, and motherhood for several African animals including African elephant, Burchell's zebra, Cape buffalo, Defassa waterbuck, impala, and Uganda kob. Between 24 and 45 percent of the variation in vigilance behavior was accounted for by location (center or edge of herd), sex, age and whether a female had young. Time of day entered the linear multiple regression models for two species, and surprisingly group size did not enter any of the linear multiple regression models in 1993. In general, females with young were more vigilant than their young or females without young. There were few gender differences in vigilance among animals without young, except that male zebra, wildebeest and waterbuck were more vigilant than females. Animals on the edge of herds devoted more time to vigilance than intermediate or central animals (regardless of sex or age class). Although there was no relationship between group size and vigilance in 1993 when all herds were considered, there was a decrease in vigilance with increasing herd size for impala and kob for herds less than 50. Moveover, herd size and vigilance were negatively correlated in our 1984-1985 study, due partly to differences in group sizes. In 1984-1985 animals were not migrating, and were in relatively small, discrete groups, whereas in 1993 some species were migrating in large herds that stretched for several km. We suggest that in 1993 herd size was above a threshold where increases in group size can lead to further decreases in vigilance. Under these circumstances, location in the herd becomes paramount: Outside animals can be directly exposed to attack. Consequently animals on the edge devote more time to vigilance than central animals.

One of the most striking aspects of animal groups is their remarkable variation in size, both within and between species. While a number of mechanistic models have been proposed to explain this variation, there are few comprehensive datasets against which these models have been tested. In particular, we only vaguely understand how environmental factors and behavioral activities affect group-size distributions. Here we use observations of House sparrows (Passer domesticus) to investigate the factors determining group-size distribution. Over a wide range of conditions, we observed that animal group sizes followed a single parameter distribution known as the logarithmic distribution. This single parameter is the mean group size experienced by a randomly chosen individual (including the individual itself). For sparrows, the experienced mean group size, and hence the distribution, was affected by four factors: morning temperature, place, behavior and the degree of food spillage. Our results further indicate that the sparrows regulate the mean group size they experience, either by groups splitting more or merging less when local densities are high. We suggest that the mean experienced group size provides a simple but general tool for assessing the ecology and evolution of grouping.

Increasing elk (Cervus elaphus nelsoni) populations across the West in response to increased demand for recreational and hunting opportunities may have negative, unintended consequences for disease transmission risk. Historically, free-ranging elk populations were not thought to sustain brucellosis (Brucella abortus), but recent studies suggest increasing elk densities may result in free-ranging elk serving as maintenance hosts for the disease. We evaluated spatial variation in elk density, group sizes, and adult female brucellosis seroprevalence in 39 elk management districts in the Greater Yellowstone Ecosystem using a Bayesian approach. We used modeled relationships to estimate the effects of reducing elk density by 10–90% on grouping patterns and seroprevalence rates. Reducing the density of the 3 highest density elk herds by 10%, 50%, and 90% was predicted to result in a 9%, 39%, and 59% decrease in mean group size, whereas reducing the density of the 3 lowest density elk herds was predicted to result in only a 0%, 0.7%, and 1.3% decrease in mean group size. We estimated seroprevalence rates of 0.01–0.27 across management districts, and seroprevalence increased as elk density increased. For the 7 of 39 management districts with >10% estimated seroprevalence, 10%, 50%, and 90% reductions in elk density resulted in predicted mean seroprevalence reductions of 2%, 7%, and 9%, respectively. For the 14 management districts with ≤1% estimated seroprevalence, 10%, 50%, and 90% reductions in elk density resulted in no measurable change in predicted mean seroprevalence. Our results suggest that elk density has an important effect on elk group sizes, which may influence the risk of brucellosis transmission and resultant exposure rates. Manipulating elk density may in turn affect brucellosis seroprevalence rates. However, debate among the diverse stakeholders involved in elk management on the effectiveness of reducing density, group sizes, and brucellosis exposure rates in elk, relative to other interests and objectives, is necessary prior to manipulation of elk density for this purpose. © 2015 The Wildlife Society.

As part of the evidence for his hypothesis that the Tsavo elephant (Loxodonta africana (Blumenbach)) population was subdivided into about ten discrete units, Laws (1969a) indicated pronounced differences in mean group size between some of the 'unit populations' (Laws 1969a, Fig. 2). Casual observations and a preliminary examination of group size data from several aerial counts suggested that mean group size varied considerably over time in any one area and that elephants tended to aggregate, during the rainy season, into fairly large assemblages that broke up again as the dry season progressed. Similar observations have been made in other areas, e.g. the Serengeti (Hendrichs 1971; Douglas-Hamilton 1972). Laws' conclusions were based on about one year's field work only; their validity has already been questioned on the basis of records on movements of individual elephants (Leuthold & Sale 1973). The present study was therefore undertaken with the dual objective of (a) re-examining Laws' hypothesis of the existence of discrete 'unit populations', each with its own social structure, through an analysis of group size data from various sources and (b) identifying possible patterns of variation in mean group size and the factors underlying them.

An adult female African forest buffalo (Syncerus caffer nanus) of unknown age was presented with signs of recurrent hoof overgrowth, persistent anestrous, obesity, dull hair coat, and decreased activity level. Complete blood counts and serum biochemistry values were unremarkable. Decreased concentrations of total triiodothyronine and total thyroxine were noted compared with values for normal domestic cattle and a healthy African forest buffalo. Treatment with oral levothyroxine increased blood concentrations of total triiodothyronine and total thyroxine, and subsequent improvement in clinical signs included weight loss, hair regrowth, and reproductive cycling.

The forest buffalo (Syncerus caffer nanus) typically inhabits the dense rain forests of western and central Africa. We recorded the 1st data on the behavior and social interactions of forest buffalo in natural forest clearings that represent crucial places in the rain forest for feeding and social interactions among individuals. Data were collected from a buffalo herd during January 2002–January 2004 in the Bai-Hokou study area (Dzanga-Ndoki National Park, Central African Republic). We analyzed typical behaviors (i.e., grazing, resting or ruminating, and moving) of both the herd and individuals (from 16 to 24 buffalos), as well as the most frequent social interactions. Spatial distribution among buffalos in the herd, related to both distance from forest edge and to the season (wet versus dry seasons), showed that the adult male was commonly closer to the females than to juveniles. Individuals were generally further away from each other when in the vicinity of the forest edge. Moreover, at greater distances from the forest edge, the number of buffalos in the herd increased. During the wet season, the herd was generally smaller and individuals were more spread out within the same clearing. The most common behavior of the male, females, and juveniles was resting or ruminating. Behavioral interactions by adults were mainly addressed to juveniles.

Chital or axis deer (Axis axis) form fluid groups that change in size temporally and in relation to habitat. Predictions of hypotheses relating animal density, rainfall, habitat structure, and breeding seasonality, to changes in chital group size were assessed simultaneously using multiple regression models of monthly data collected over a 2 yr period in Guindy National Park, in southern India. Over 2,700 detections of chital groups were made during four seasons in three habitats (forest, scrubland and grassland). In scrubland and grassland, chital group size was positively related to animal density, which increased with rainfall. This suggests that in these habitats, chital density increases in relation to food availability, and group sizes increase due to higher encounter rate and fusion of groups. The density of chital in forest was inversely related to rainfall, but positively to the number of fruiting tree species and availability of fallen litter, their forage in this habitat. There was little change in mean group size in the forest, although chital density more than doubled during the dry season and summer. Dispersion of food items or the closed nature of the forest may preclude formation of larger groups. At low densities, group sizes in all three habitats were similar. Group sizes increased with chital density in scrubland and grassland, but more rapidly in the latter—leading to a positive relationship between openness and mean group size at higher densities. It is not clear, however, that this relationship is solely because of the influence of habitat structure. The rutting index (monthly percentage of adult males in hard antler) was positively related to mean group size in forest and scrubland, probably reflecting the increase in group size due to solitary males joining with females during the rut. The fission-fusion system of group formation in chital is thus interactively influenced by several factors. Aspects that need further study, such as interannual variability, are highlighted.

A 2-yr-old female forest buffalo (Syncerus caffer nanus) presented with acute trauma to the right horn following a fight with a conspecific resulting in fracture and avulsion of the frontal bone, cornual process, horn, and juxtaposed skin. The animal was sedated for wound care and debridement followed by placement of an antibacterial-impregnated polymethylmethacrylate (PMMA) dressing. The dressing was noted to be intact on examination at day 7 post-injury, but had become dislodged and had to be replaced at day 11 postinjury. The replacement dressing ultimately fell off 68 days post-injury, revealing a healed circular scar. The use of PMMA in this case provided optimal wound care. In the 6 yr since the injury, the animal has grown a nearly normal-appearing horn, suggesting that the noncornual skin and associated skull structures may retain the ability to differentiate into a near-normal appearing horn because the entire horn apparatus in this case was avulsed.

Vector-borne and zoonotic pathogens have comprised a significant proportion of the emerging infectious diseases in humans in recent decades. The role of many wildlife species as reservoirs for arthropod-borne viral pathogens is poorly understood. We investigated the exposure history of various African wildlife species from the Congo basin to mosquito-borne flaviviruses and alphaviruses by testing archived serum samples. Sera from 24 African forest buffalo (Syncerus caffer nanus), 34 African elephants (Loxodonta africana), 40 duikers (Cephalophus and Philantomba spp.), 25 mandrills (Mandrillus sphinx), 32 mountain gorillas (Gorilla beringei beringei), five Grauer's gorillas (Gorilla beringei graueri), two L'Hoest's monkeys (Cercopithecus lhoesti), two golden monkeys (Cercopithecus kandti), and three chimpanzees (Pan troglodytes) sampled between 1991 and 2009 were tested for antibodies against chikungunya virus (CHIKV), o'nyong-nyong virus (ONNV), West Nile virus (WNV), dengue 2 virus (DENV-2), and yellow fever virus (YFV) by plaque reduction neutralization test. Specific neutralizing antibodies against ONNV were found in African forest buffalo in the Democratic Republic of the Congo (DRC) and Gabon, duikers in the DRC, and mandrills in Gabon, providing novel evidence of enzootic circulation of ONNV in these countries. African forest buffalo in the DRC and Gabon also demonstrated evidence of exposure to CHIKV, WNV, and DENV-2, while mandrills in Gabon were antibody positive for CHIKV, DENV-2, WNV, and YFV. All of the elephants tested had a strong neutralizing antibody response to WNV. We also document results from a survey of gorillas for arboviruses, of which 4/32 (13%) had antibody to an alphavirus or flavivirus. Overall, our results demonstrate a high prevalence of neutralizing antibodies against multiple arboviruses in wildlife in equatorial Africa.

This study examines the effect of a clumped, non-defendable and abundant year-round food resource (Cape fur seals) for black-backed jackal Canis mesomelas social structure and spatial organization at Cape Cross Seal Reserve and the National West Coast Recreation Area in Namibia during the jackals' denning period in 2004 and 2005. Geo-referenced observations of behaviour and space-use were used to test for territoriality, and to assess commuting distances, territory size, group size and within-territory density on the Namibian coast. Jackals displayed behaviour indicative of territoriality to within 50 m of the fur seal colony. In accordance with optimal foraging theory, jackals commuted between 0.45 and 20.03 km from their territory (low prey availability) to the seal colony (high prey availability). The observed within-population variation in group size (two to eight adults), territory size (0.20–11.11 km2) and within-territory density (0.31–9.80 jackals km?2) was unprecedented and strongly associated with distance from the food resource. Group and territory size increased, while within-territory density declined with increasing distance from the fur seal colony. We discuss the relative importance of the food resource and other factors in determining jackal social and spatial organization.

Population status, group composition and social organization of the Soemmerring's gazelle ( Gazella soemmeringii ) were studied at Awash National Park (ANP) and Alledeghi Wildlife Reserve (AWR) in 2000. Total count method was used to assess the population size of the gazelle. Thirteen routes, each route being two kilometres away from the other, were designated at AWR for the vehicle survey. Similarly, 10 routes, each being one kilometre away from the other, were designated at ANP. The results revealed a mean population of 457.8 individuals in the selected study site in Alledeghi Wildlife Reserve, and 41.45 in Ilala Sala. Grouping pattern showed that cohesion was stronger. The large females group containing juveniles and of adult males were the two main social units. Mean group size in ANP was 4.4 whereas that of AWR was 16.8 individuals (p>0.001). A paired-sample t-test comparison of the total frequency of categories of the group sizes for the two areas showed a significant difference (p=0.026). Local variation in group size did exist in AWR (p=0.021). But this variable showed no significant difference (p= 0.414) in ANP. Herds of 6–10 were most common at Ilala Sala and 20–50 at AWR. However, herd size ranges from 3–250 individuals at AWR. Comparing seasonal variations in group sizes showed no significant difference. It is presumed that alteration of the original habitats might have an effect on the group pattern and social organization of study population as observed from one of the study site. Keywords : abundance, Alledeghi Wildlife Reserve, Awash National Park, group size, Soemmerring's gazelle SINET: Ethiopian Journal of Science Vol. 28(2) 2005: 161-170