Fire induced changes in the foraging behaviour of impala Aepyceros melampus in Lake Mburo National Park, Uganda

The impact of fire on the foraging behaviour of impala (Aepyceros melampus), was studied in the Lake Mburo National Park, Uganda. Two indices of foraging efficiency were used to establish differences in feeding behaviour in burnt and unburnt control areas. These are acceptable grass/browse abundance (AGA/ABA), expressed in terms of feeding time achieved per 50 steps and food ingestion rate (FIR), expressed as the cumulative percentage. Accumulation of above ground grass biomass was also measured in burnt and control areas. After burning, the grazing efficiency remains constant throughout the dry season, while the browsing time achieved per 50 steps decreases drastically. In the control areas AGA decreased with increasing length of the dry season while ABA increased. When expressed in terms of cumulative percentage (FIR), the results show a significant increase of 31% in foraging time spent grazing and a 24% decrease in foraging time spent browsing, in burnt areas. The results confirm the classification of impalas as intermediate or mixed feeders with a distinct preference for grass. Impala foraging patterns after burning are discussed and compared with investigations on the effect of burning on the behaviour of impalas and Buffon's kob (Kobus kob kob) in other areas of Africa.     

Sexual,Seasonal and Group Size Differences in the Allocation of Time between Vigilance and Feeding in the Greater Rhea,Rhea americana

We studied the effect of sex and group size on the proportion of time a greater rhea, Rhea americana, allocates to vigilance and feeding during the breeding and the non-breeding seasons. We analysed 175 records of focal animals that were feeding alone or in groups of 2 to 26 birds. In both seasons, males spent more time in vigilance and less time in feeding than females. Both sexes spent more time in vigilance and less time in feeding during the breeding season. Sexual and seasonal differences in vigilance were the result of different mechanisms. Males had shorter feeding bouts than females but there were no sexual differences in the length of the vigilance bouts. On the contrary, seasonal differences were the result of males and females having longer vigilance bouts during the breeding season but there were no seasonal differences in the length of the feeding bouts. During the non-breeding season, individual vigilance was higher in rheas foraging alone than in groups. In this case, solitary birds had longer vigilance and shorter feeding bouts than birds foraging in groups. We discuss the possible effect of intragroup competition and food availability on the allocation of time between feeding and vigilance in this species.     

Effects of seasonal variation in prey abundance on field metabolism, water flux, and activity of a tropical ambush foraging snake

The responses of animals to seasonal food shortages can have important consequences for population dynamics and the structure and function of food webs. We investigated how an ambush foraging snake, the northern death adder Acanthophis praelongus, responds to seasonal fluctuations in prey availability in its tropical environment. In the dry season, field metabolic rates and water flux, as measured by doubly labeled water, were significantly lower than in the wet season. Unlike some other reptiles of the wet-dry tropics, death adders showed no seasonal difference in their resting metabolism. About 94% of the decrease in energy expended in the dry season was due to a decrease in activity and digestion, with lower body temperatures accounting for the remainder. In the dry season, death adders were less active and moved shorter distances between foraging sites than in the wet season. Analysis of energy expenditure suggested that adders fed no more than every 2-3 wk in the dry season but fed more frequently during the wet season. Unlike many lizards that cease feeding during the dry season, death adders remain active and attempt to maximize their energy intake year-round.     

Effect of Seasonality on the Behavior of an Insectivorous Primate, Tarsius spectrum

The distribution and quality of food resources is generally recognized as the preeminent factor explaining much interspecific and intraspecific variation in the behavior of nonhuman primates. Primates that live in seasonal environments often show predictable responses to fluctuating resources. In order to compensate for the reduction in resource availability, primates variously switch to alternative, poorer quality food sources, increase the amount of time they spend foraging, or increase their daily path length. Some primate species reduce their group size or maximize the group dispersion. I address whether spectral tarsiers (Tarsius spectrum), which are insectivores, modify their behavior in the same ways as frugivores and folivores in response to seasonal or scarce resources. My results indicate that wild spectral tarsiers modify their activity budget in response to seasonal resources. Specifically, during periods of low resource availability, spectral tarsier males and females spent more time traveling and foraging compared to their activity budget during the wet season. Males and females not only increased the amount of time they spent foraging during times of low resource abundance but also modified their foraging behavior. During the wet season, when resource abundance was high, they consumed Orthoptera and Lepidoptera with greater frequency than during the dry season. During the dry season, when resource abundance was low, spectral tarsiers still ate numerous Orthoptera and Lepidoptera, but they also increased consumption of Coleoptera and Hymenoptera. Spectral tarsiers were also more likely to be involved in territorial disputes during the dry season than during the wet season. Intragroup encounters decreased in frequency in the dry season versus the frequency of encounters during the wet season.     

The foraging ecology of feral goats

Feral goats (Capra hircus) were studied in the Mahoenui giant weta reserve, southern King Country, New Zealand, from March 1992 to February 1993. The reserve supports the main population of the undescribed Mahoenui giant weta (Deinacrida sp.). Gorse (Ulex europaeus) is the dominant woody browse plant in the reserve and provides protection, shelter and food for weta. The activities, foraging behaviour and diet of feral goats within the reserve were measured by direct observation and analysis of rumen contents. Measures of nutrient levels indicate that gorse is adequate for goat growth only during late spring/summer, and becomes a maintenance food at other times of the year. Feeding (grazing and browsing) was the dominant activity of adult feral goats in the reserve. Females spent more time feeding than males. Grazing and browsing changed seasonally for both sexes, with grazing generally decreasing from autumn to summer, and browsing increasing from summer to spring. In every season females spent more time grazing than males, but males browsed more than females. Greater use of browse by males may be an effect of the presence of females. Browsing of gorse by goats may not be an important influence on weta survival.     

Time budget of the green monkey,Cercopithecus sabaeus: Some optimal strategies

Members of a single group of green monkeys spent, on average, 44.8% of their waking time foraging, 46.7% resting, and 8.5% in social activities, over 1 year. There was significant variation in activity budgets over months (ranging from 35 to 55% of the time spent feeding). Diurnal rhythms of feeding and ranging were influenced by the daily cycle of temperature in predictable ways in different seasons: in the dry season, activity was reduced if it was too hot or too cold, while the temperature in the wet season did not affect activities. Feeding was also synchronized among individuals on a finer time scale, irrespective of the time of day. There was closer synchrony when feeding on less common foods. An ecological model of foraging time and energetics was tested, using estimates of the costs and benefits of foraging and predicting how these are optimally balanced in relation to the food density. Both feeding time and distance traveled increased as food availability increased. Costs and benefits were balanced over several days. Comparisons between populations of Cercopithecus aethiopswere made; differences in time budgets were compared with differences in the availability and quality of food. Insufficient comparative data are available for firm conclusions about the role of different energetic and nutritive strategies in population differences.     

Effects of body size on the diurnal activity budgets of African browsing ruminants

We compared the diurnal activity budgets of four syntopic species of African browsing ruminant that differ widely in body size. These were concurrently studied through all phases of the seasonal cycle, in the same area, using the same methods. We tested five predictions from the literature on how body size is expected to influence the behaviour of tropical ungulates: the smallest members of the browsing ruminant guild exhibit (1) the lowest allocation of diurnal time to activity; (2) the greatest hour-to-hour variation in activity and resting time; (3) the greatest reduction in activity time during the hottest days; (4) the least change between wet and the dry seasons in the ratio of feeding: ruminating time; and (5) the greatest time budget allocation to vigilance. Prediction 1 was supported in that the smaller species spent less time being active during the day. Prediction 2 was also supported in that the smaller species were more variable in their relative allocations of time to activity and resting through successive hours of the day. Contrary to Prediction 3, however, the greatest reduction in activity with increasing temperature was found for the largest guild member. The smaller species can achieve their daily food intake requirements by feeding at night and in the cool hours of the day, while the larger species have to feed during all hours of the day and are thus more susceptible to thermoregulatory constraints on foraging. Prediction 4 was partially upheld in that the largest species (giraffe) displayed the widest variation in feeding: ruminating time through the seasonal cycle. Prediction 5 was not supported, indicating that multiple factors interact with body size in determining vigilance behaviour.     

Seasonal Variation in the Activity Patterns and Time Budgets of <Emphasis Type="Italic">Trachypithecus francoisi</Emphasis> in the Nonggang Nature Reserve,China

Activity patterns and time budgets are 2 important aspects of animal behavior that researchers use to investigate ecological influences on individual behavior. We collected data on activity patterns and time budgets in 1 group of François’ langurs (Trachypithecus francoisi) from August 2003 to July 2004 in the Nonggang Nature Reserve, Guangxi Province, China, via instantaneous scan sampling method with 15-min intervals. The diurnal activity pattern of François’ langurs showed morning and afternoon feeding peaks, with a midday resting peak. Seasonal change was apparent in the activity pattern: 2 significant feeding peaks occurred in the dry season and only 1 significant feeding peak in the rainy season. The group spent an average of 51.5% of the daytime resting. Feeding and moving accounted on average for 23.1% and 17.3% of the activity budget, respectively. Subjects spent little time on social activities, averaging 2% for grooming and 5.5% for playing. Their time budgets showed significant seasonal variation: they spent a greater proportion of time on feeding and less time on resting and grooming in the dry season than in the rainy season. They also differed among different sex-age classes: immatures spent more time playing, whereas adults devoted more time to resting, feeding, and grooming. Correlations between time budgets and food items or food availability clearly indicated that François’ langurs might adopt an energy-maximizing strategy when preferred foods were scarce in the dry season.     

The Effect of Climatic Factors on the Activity Budgets of Barbary Macaques (Macaca sylvanus)

Climatic conditions can significantly affect the behavior of animals and constrain their activity or geographic distribution. Barbary macaques (Macaca sylvanus) are one of the few primates that live outside the tropics. Here we analyze if and how the activity budgets of Barbary macaques are affected by climatic variables, i.e., air temperature, relative humidity, rainfall, and snow coverage. We collected scan sampling data on the activity budgets of four groups of macaques living in the Middle Atlas Mountains of Morocco from June 2008 to January 2011. This habitat is characterized by extreme seasonal changes, from cold and snowy winters to hot and dry summers. The activity budgets of the macaques differed across months but not across the time of day (with the exception of time spent feeding). The monkeys spent significantly more time feeding or foraging when there was no snow than when snow coverage was moderate or major. Daily rainfall was positively related to resting time and negatively to time spent moving or in social behavior. Air temperature was negatively related to time spent feeding or foraging. Finally, time spent on social behavior was significantly lower when relative humidity was high. These data indicate that environmental factors significantly affect the time budgets of endangered Barbary macaques, a species that has been little studied in the wild. Our findings support previous studies on temperate primates in showing that snow coverage can have negative consequences on the feeding ecology and survival of these species.     

The effect of urban and rural habitats and resource type on activity budgets of commensal rhesus macaques (Macaca mulatta) in Bangladesh

Macaques are characterized by their wide distribution and ability to adapt to a variety of habitats. Activity budgets are affected by habitat type, season, and food availability in relation to differing age–sex class and individual requirements. We conducted a comparative study on two commensal rhesus groups, one living in a rural village and the other in the center of urban Dhaka, Bangladesh. The study was conducted in three different seasons between 2007 and 2009 in order to evaluate how habitat type and season affects their behavioral activities. Differences in food type and its availability between these two habitats were mainly responsible for the variations in activity budgets between groups. Feeding time in the rural group was significantly longer than that in the urban group. In contrast, grooming and object manipulation/play were significantly greater in the urban than the rural group. Seasonal variations in all major behaviors were significantly affected by group, with more time spent feeding in summer than in winter/dry season, and more time spent grooming and moving in winter/dry season than summer in the rural group. In contrast, time spent resting was greater in the monsoon and summer seasons than the winter/dry season in the urban group. Grooming time was greater in the winter/dry season than the monsoon and summer seasons. In both groups, immature of both sexes spent significantly more time on feeding and object manipulation/playing and less time resting than adults. Adult females spent more time grooming than males and immatures, of both sexes, in both groups. Moreover, the rural group spent most of their time feeding on garden/crop produce and wild plant food resources, while the urban group spent more time feeding on provisioned foods. These results showed that differences in the activity budgets of rural and urban dwelling macaques were due largely to the differences in available food resources. Commensal rhesus macaques show a high degree of behavioral flexibility in response to habitat and resource variability, and knowledge of these differences is important for the conservation and management of highly commensal primates.     

Seasonal Effects on Play Behavior in Immature <Emphasis Type="Italic">Saimiri sciureus</Emphasis> in Eastern Amazonia

Play behavior is prevalent among most mammalian young, particularly primates. Though several hypotheses address the function of play, researchers have documented information on the potential costs of play and of environmental effects on the occurrence of primate play less well during long-term field studies. I examine seasonal changes in play behavior of immature squirrel monkeys (Saimiri sciureus) across 4 age classes: infants, young juveniles, mid-juveniles, and late juveniles. I observed individuals during 12 mo in Eastern Brazilian Amazonia, an area characterized by highly seasonal rainfall. Play was strongly tied to seasonality, food availability, and changes in diet. The percentage of time spent playing was reduced in the dry season, a period characterized by low fruit availability and an increase in time spent foraging for prey. I suggest that the decrease in play behavior in the dry season is related both to a higher need for energy conservation and to increased time expended in foraging activities.     

Foraging strategies and seasonal diet optimization of muskoxen in West Greenland

Various aspects of optimal foraging and seasonal diet composition of bulls (bachelor and dominant), cows, subadults, and yearlings of muskoxen Ovibos moschatus were investigated in West Greenland during the following seasons: calving, post-calving, summer, rut and mid-winter. The following hypotheses were tested: (1) muskoxen maximize daily energy intake during spring and summer, (2) dominant bulls monopolizing cows during the rutting season shift from an energy maximizing to a time minimizing foraging strategy in order to maximize the time available for reproductive activities, and (3) muskoxen employ a time minimizing foraging strategy during winter to conserve energy. As forage quality changed throughout the short Arctic growing season, muskoxen responded by changing the proportions of daily time spent feeding on graminoids (Cyperaceae, Poaceae) and dicots (Salix, Betula), respectively. This seasonal variation in the relative proportion of daily feeding time spent ingesting graminoids followed approximately the energy maximization prediction over the periods calving to rut. Neither time minimizing nor random foraging could explain the observed diets in this period, thus confirming hypothesis 1. Dominant bulls did not shift to the time minimizing strategy as predicted by hypothesis 2. However, during the pre-rutting and rutting seasons bulls deviated from the other sex/age classes by failing to obtain the daily maximum energy predicted by the model, as a result of a higher proportion of time allocated to agonistic and sexual behaviour. During winter, none of the sex/age classes employed a time minimizing strategy, so rejecting hypothesis 3. Instead, muskoxen were found to maximize Na intake, indicating that Na is of major importance for winter survival. The results emerging from a linear programming model with constraint settings varying over seasons confirm that the constraint parameters applied are indeed important limiting factors for muskoxen in natural populations.     

Responses of squirrel monkeys to seasonal changes in food availability in an eastern Amazonian forest

Tropical forests are characterized by marked temporal and spatial variation in productivity, and many primates face foraging problems associated with seasonal shifts in fruit availability. In this study, I examined seasonal changes in diet and foraging behaviors of two groups of squirrel monkeys (Saimiri sciureus), studied for 12 months in Eastern Brazilian Amazonia, an area characterized by seasonal rainfall. Squirrel monkeys were primarily insectivorous (79% of feeding and foraging time), with fruit consumption highest during the rainy season. Although monkeys fed from 68 plant species, fruit of Attalea maripa palms accounted for 28% of annual fruit-feeding records. Dietary shifts in the dry season were correlated with a decline in ripe A. maripa fruits. Despite pronounced seasonal variation in rainfall and fruit abundance, foraging efficiency, travel time, and distance traveled remained stable between seasons. Instead, squirrel monkeys at this Eastern Amazonian site primarily dealt with the seasonal decline in fruit by showing dietary flexibility. Consumption of insects, flowers, and exudates increased during the dry season. In particular, their foraging behavior at this time strongly resembled that of tamarins (Saguinus sp.) and consisted of heavy use of seed-pod exudates and specialized foraging on large-bodied orthopterans near the forest floor. Comparisons with squirrel monkeys at other locations indicate that, across their geographic range, Saimiri use a variety of behavioral tactics during reduced periods of fruit availability.     

Subgrouping Patterns in a Group of Wild <Emphasis Type="Italic">Cebus apella nigritus</Emphasis>

Seasonal patterns of group fragmentation, including the size of subgroups and percentage of time spent in subgroups, may provide information on individual decision-making in response to resource distribution. Age-sex class composition of subgroup membership can offer insights into the social dynamics of the group as a whole. At most field sites, capuchins (Cebus spp.) form stable groups with no evidence of group fragmentation. Here I describe seasonal subgrouping patterns, including proportion of time spent in subgroups, subgroup size, age-sex membership, dyadic fidelity, stability of membership, and the effect of subgrouping on individual foraging efficiency, in a group of wild Cebus apella nigritus. From September 1996 to August 1997 the study group at the Estação Biológica de Caratinga, Brazil divided into 148 different subgroups, on 99 of 194 census days. In contrast to expectations for subgrouping patterns as a response to seasonal distribution of resources, the proportion of days spent in subgroups did not vary significantly by season. Subgroup composition was relatively fluid, with multimale multifemale subgroups the most common throughout the year. Unimale multifemale subgroups were restricted to the wet season; in contrast, all-male subgroups and unimale unifemale subgroups occurred in the dry season. For both males and females, low rank predicted membership in smaller subgroups. For males, but not females, subgrouping coincided with increased foraging efficiency, as measured by increased time spent ingesting food and decreased time spent traveling on days with subgrouping compared to days with the group in a cohesive unit.     

Sex and size related differences in the dry season feeding patterns of elephants in Chobe National Park, Botswana

Differences in feeding patterns of the African elephant were examined by sex and age during the dry season in a dystrophic savanna-woodland ecosystem in northern Botswana. Adult males had the least diverse diet in terms of woody plant species, but they consumed more plant parts than family units. The diameter of stems of food plants broken or bitten off was also greater for adult males than for females and subadult males. Adult males spent more time foraging on each woody plant than did females. The number of woody plant species and individuals present were higher at feeding sites of family units than at feeding sites of adult males, indicating that family units positioned themselves at feeding sites with higher species diversity than those of males. We argue that the most likely explanation for these differences is related to the pronounced sexual size dimorphism exhibited by elephants, resulting in sex differences in browsing patterns due to the allometric relationships that govern the tolerance of herbivores for variation in diet quality. From our results this Body Size Hypothesis is accepted rather than the alternative Scramble Competition Hypothesis, which predicts that adult male elephants consume lower quality browse because they are displaced from preferred browse as an outcome of scramble competition with adult females and their offspring. If the feeding patterns of adult male elephants were affected by intersexual scramble competition, we would expect adult males to browse at a higher level in the canopy than the smaller-bodied females and their offspring. No evidence was found for this, although adult females were found to browse at a higher level in the canopy when feeding in close proximity to subadults and juveniles than when feeding alone. Sex differences in elephant browsing patterns are, we propose, of relevance to understanding and managing elephant impacts on African woodlands.     

Food diversity and choice of white-headed langur in fragmented limestone hill habitat in Guangxi,China

We studied the diet and food choice of three groups of white-headed langurs (Trachypithecus leucocephalus) from July 2002 to June 2003 at Fusui Rare Animal Reserve, Guangxi, China. Data were collected from via focus group sampling, with continuous recording. A total of 109 plant species (including 19 unidentified species) were used as food by the white-headed langur. They spent 91.6% of total feeding time feeding on leaves, 4.2% on fruits and 3.3% on stems. Flowers and other food items accounted for only 0.3% and 0.6% of total feeding time, respectively. There were significant seasonal variations in the langurs’ diets with changes in the total number of species and the diversity of food species consumed. The langurs used significantly more plant species as food in the rainy season than in the dry season (36 species vs. 26.5 species). Dietary diversity was also significantly higher in the rainy season than in the dry season (2.6 vs. 2.4). No significant seasonal variation was found in the percentage of various plant parts in their monthly diets. Though the white-headed langur fed on many plant species, 11 species made up 84.9% of their diet. There were no significant correlations between the percentage of feeding time for main food plant species and their corresponding abundance in the habitat, content of water, crude protein, crude fiber and the ratio of crude protein to crude fiber. These results suggest that food choice of the white-headed langur is not influenced by their abundance and nutritional content.     

Seasonal variation in patch use in a tropical African environment

We used giving-up densities (GUD) to study patch use decisions of small granivorous passerines throughout the year. We measured GUDs continuously in four sites for a period of 9–10 months per year during 2004 and 2005 in a savannah area in Jos, central Nigeria. The study thus covered a period from the middle of the dry season, through the wet season to the beginning of the next dry season in each year. We placed experimental food patches in both open areas and in cover to investigate possible effects of predation risk and thermal hazard on the foraging behavior of the birds. We found a difference in GUDs between the microhabitats, with a consistently lower GUD in cover throughout the year and for the two years. During both years GUDs followed a pattern coinciding with the seasonal change in local seed availability. An initial decline in GUDs late in the dry season was followed by a steady increase during and after the rains. A similar trend in GUDs observed for both years supports the conclusion that GUDs measure the feeding birds' assessment of environmental quality, possibly in combination with other factors changing predictably during the year. We conclude that food abundance may act with other environmental and ecological factors to affect foraging decisions throughout the year.     

Seasonal Variation in the Activity and Dietary Budgets of Cat Ba Langurs (<Emphasis Type="Italic">Trachypithecus poliocephalus</Emphasis>)

Primate activity budgets are dictated by food availability and distribution; thus primates living in seasonal environments must adapt their behaviors to accommodate fluctuations in resources. Cat Ba langurs (Trachypithecus poliocephalus), a Critically Endangered Asian colobine and a member of the limestone langur group (francoisi superspecies group within genus Trachypithecus), live only in fragmented and disturbed habitats on Cat Ba Island, northeastern Vietnam. This study aimed to assess the behaviors and diet of Cat Ba langurs by group, age, sex, and season. We predicted they would have high rates of inactivity and foraging, low rates of social behaviors, with seasonal variation that reflects an energy-maximizing strategy. We conducted behavioral observations through scan sampling over an 11-month period and found that Cat Ba langurs spent a significant portion of their day inactive (57 %) followed by foraging (18 %), socializing (13 %), locomoting (10 %), and engaging in “other” behaviors (2 %). Their diet was made up primarily of leaves (83 %) followed by flowers (8 %), fruit (6 %), and stems (3 %). We found groups to differ in diet and activity, which is likely owing to differences in demographics and home range between groups. Seasonally, the animals ate more leaves and spent more time foraging in the dry season than the wet season, suggesting that they are energy maximizers. Cat Ba langurs have activity and dietary budgets similar to those of other limestone langurs, and respond to a presumed seasonal fluctuation in food availability similarly.     

Influence of Dry Season and Food Quality and Quantity on Behavior and Feeding Strategy of Propithecus verreauxi in Kirindy, Madagascar

According to optimal foraging theory, herbivores can base food choice mainly on the quality or the quantity of food, or both. Among herbivorous primates, folivorous lemurs living in the highly seasonal environment of Madagascar have to cope with the shortage of high-quality food during the dry season, at least in deciduous forests. We studied (Verreaux's sifaka) in Kirindy, western Madagascar, to understand the influence of dry season and food quality and quantity on behavioral patterns and feeding strategy (qualitative vs. quantitative dietary choice) of a folivorous lemur in a deciduous forest. We followed 7 groups (4 groups/period; 3 individuals/group/month) during 4 periods of the year (wet season: February–March; early/middle/late dry season: May–June; July–September; October–November). We collected samples of plants eaten and examined behavioral and feeding patterns, considering food quality (macronutrients, proteins/fibers ratio, and tannins) and abundance. We found 1) a significant reduction of home range, core area, and daily path length from the wet to the dry season, possibly related to dietary change and 2) a daily period of inactivity in the dry season for energy conservation. Regarding the feeding strategy, Kirindy sifakas showed 1) high variation and selection in choosing food items and 2) a dietary choice based mainly on quality: Kirindy sifakas fed on plant species/families independently from their abundance and tannins represented a feeding deterrent during the dry season. Overall, behavioral and dietary adaptations allow Kirindy sifakas to overcome the shortage of high-quality food in the lean period.