Home range, home range overlap, and species energy use among herbivorous mammals

Harestad & Bunnell (1979) showed that, at least for North American species, home ranges of large herbivorous mammals are relatively larger than we would expect on metabolic grounds, and suggested that the productivity of the environment for mammal species decreases with increasing body size. This interpretation assumes that the number of conspecifics that share an individual's home range is independent of body size. Data presented here show that this is not true for the species in their sample; the home range is shared with an increasing number of conspecifics in larger herbivore species. The productivity of the environment for a species is independent of body size and the area available to an individual for its own use scales approximately as do individual metabolic requirements. These results agree with conclusions based upon the scaling of population density with body mass and illustrate the interrelationship between home range and dietary and social organization trends among mammalian herbivores. Individual home range area is a function of the way in which the local population of a species, not merely an individual, exploits the environment.     

Foraging, home range use and social behaviour of a group-living rainforest raptor, the Red-throated Caracara Daptrius americanus

A stable group of six Red-throated Caracaras Daptrius americanus was followed over 5 years in a rainforest area of French Guiana and was intensively studied during 52 days in 1989-90. They bred successfully only twice (1986 and 1990). Communal nest guarding and brood care were observed. Their social behaviour and group-living habits seem unique among raptors. The 400-ha all-purpose, year-round, group territory was defended by all individuals and was almost fully used. The birds foraged individually, but the cohesion of the group and its coordinated movements were maintained by periodic loud rallying calls. Food sharing of large prey items and even deliberate allofeeding also contributed to the group cohesion. Mature, high, closed-canopy forest was preferred and 88% of the actively foraging birds were encountered in the understorey, where they had a higher success rate than those hunting in the upper canopy. This may explain why the species' frequency and group size markedly decreased in secondary or disturbed forests. The 12-hour daily activity period was reduced by an average of 2 hours either by a midday pause (hot weather) or by rains. At least 74% of all food items taken were wasp nests or other insect nests in the foliage, 9% were hard fruits, and the remaining captures were various invertebrates or unidentified items. When the caracaras were raiding a wasp nest, the wasps were kept off probably by a powerful repellent, a striking adaptation unprecedented among birds. Several species of mostly large canopy frugivores regularly formed close associations with the caracaras to forage in the understorey, where they otherwise rarely or never ventured. This new interspecific flocking behaviour is interpreted as an antipredator strategy benefiting from the raptors' warning and mobbing efficiency.     

The predatory behaviour of a tramp ant species in its native range

Workers of the pest ant Paratrechina longicornis participate in a type of group hunting. Each individual forages with its long antennae wide open and moves quickly (6.3 cm/s) along an erratic path surrounded by nestmates behaving in the same way and within range of a recruiting pheromone. They detect prey by contact with successful workers singly capturing and retrieving small prey and seizing larger ones by an appendage. Then they recruit nestmates at short-range; all together they spread-eagle the prey and retrieve them whole.     

Interrelationships of dominance and territorial behaviour in the pupfish,Cyprinodon variegatus

Under laboratory conditions, Cyprinodon variegatus establishes either a dominance or territorial mating system. In the dominance system, one male usually has complete access to receptive females, while in the territorial system, several males have equal access. Four factors were observed to enhance a subdominant's ability to establish a territory and improve his reproductive success; increasing the number of conspecific intruders, increasing the available area, the presence of partial barrier, and the presence of a receptive female.     

A model for relating troop size and home range area in a primate species

For relating troop size (N) and home range area (R), a simple model,QR=αN, whereQ denotes habitat quality and α is a constant, was examined using published field data forMacaca fuscata, M. mulatta andColobus guereza. In particular, theN-R direct proportionality of the model was tested for its validity and usefulness in comparison with a few less simple models. The implications of the present model are discussed in relation to bioenergetics and population dynamics.     

Determinants of quality in a long-lived colonial species

1. In many animal populations a small proportion of individuals produce the majority of surviving offspring, but the underlying mechanisms are unclear. Behaviour may be an important determinant of variation in fitness: 'high-quality' individuals may have enhanced abilities in foraging or predator and parasite avoidance. 2. The role of behaviour in determining variation in quality was examined using the common guillemot Uria aalge, a monogamous seabird with biparental care. Using a novel mixed model approach, we analysed binary data on breeding success of each pair attempting to breed in each year with variables critical to breeding success (timing of breeding; inferred age; breeding experience and success; number of nest sites and partners) as fixed effects. Random effects for year, male, female and each distinct pairing of a male and a female were included in the model, allowing a quality estimate to be derived for each individual and pair. A range of behaviours associated with breeding were examined in relation to these quality estimates. 3. Breeding success declined with timing of breeding, and increased initially with age before declining in old age. It increased with previous successful experience, not breeding experience per se, until senescence effects became apparent. For males, breeding success declined with increasing numbers of mates. 4. The most important behavioural determinants of quality operated at the level of the pair, with the time mates spent together at the site and chick feeding rates both positively related to quality. At the individual level, trip durations and feeding rates were associated with female but not male quality, suggesting that pair quality was operating principally through the female. However, removal of laying date, the most important component in the binomial model, confirmed that the pair effect was much larger than the female effect. 5. This study demonstrates the potential of mixed modelling to determine quality estimates based on long-term breeding histories. The probability of a successful reproductive attempt was explained by the timing of breeding, age, successful breeding experience and number of mates. Behaviour was an important proximate mechanism underlying quality, in particular the foraging abilities of the pair, and the female's contribution to offspring provisioning. In species with biparental care, behavioural correlates of quality operate most strongly at the scale of the breeding pair, because contributions from both individuals are required for a successful outcome.     

Genetic diversity at neutral and adaptive loci determines individual fitness in a long-lived territorial bird

There is compelling evidence about the manifest effects of inbreeding depression on individual fitness and populations' risk of extinction. The majority of studies addressing inbreeding depression on wild populations are generally based on indirect measures of inbreeding using neutral markers. However, the study of functional loci, such as genes of the major histocompatibility complex (MHC), is highly recommended. MHC genes constitute an essential component of the immune system of individuals, which is directly related to individual fitness and survival. In this study, we analyse heterozygosity fitness correlations of neutral and adaptive genetic variation (22 microsatellite loci and two loci of the MHC class II, respectively) with the age of recruitment and breeding success of a decimated and geographically isolated population of a long-lived territorial vulture. Our results indicate a negative correlation between neutral genetic diversity and age of recruitment, suggesting that inbreeding may be delaying reproduction. We also found a positive correlation between functional (MHC) genetic diversity and breeding success, together with a specific positive effect of the most frequent pair of cosegregating MHC alleles in the population. Globally, our findings demonstrate that genetic depauperation in small populations has a negative impact on the individual fitness, thus increasing the populations' extinction risk.     

When individuals senesce: the 'Florida effect' on stable populations of territorial, long-lived birds

Senescence can be defined as the entire set of age-related changes that affect both vitality and function, one of which is within-individual age-related decline in reproduction. This factor is crucial for population persistence, because the senescence of individuals of a population can increase the likelihood of local extinction. Using simulations based on long-term information on a small metapopulation of a long-lived bird species, we highlight two mechanisms able to engender senescence in both breeders and floaters (i.e. non-breeding individuals) of the same population. We define 'floater shortage senescence' as breeder senescence due to low juvenile replacement rates because of high floater mortality during dispersal. Less obviously, senescence can also occur with very low floater mortality rates, and when breeding populations are remarkably free from factors that could cause catastrophic population decimation. In this scenario, low mortality in reproductive areas results in territory owners in breeding populations being characterised by progressively older breeding individuals, and old individuals waiting for a breeding opportunity: a phenomenon we refer to as the 'Florida effect'. Consistent with current views that adaptive death plays a crucial role in population dynamics, it seems reasonable to suppose that, under stable environmental conditions, the evolution of some mating mechanisms could limit the senescence of breeding individuals in a population, allowing the pool of breeding individuals to be refreshed by selection of younger breeders.     

Interactions between population processes in a cyclic species: parasites reduce autumn territorial behaviour of male red grouse

The causes of population cycles fascinate and perplex ecologist. Most work have focused on single processes, whether extrinsic or intrinsic, more rarely on how different processes might interact to cause or mould the unstable population dynamics. In red grouse (Lagopus lagopus scoticus), two causal mechanisms have been supported: territorial behaviour (changes in autumn aggressiveness) and parasites (parasite induced reduction in fecundity). Here, we report on how these two regulatory processes might interact, by testing whether the parasite suspected to cause the grouse cycles, the nematode Trichostrongylus tenuis, reduces male autumn territorial behaviour. We either treated males with an anthelmintic, to remove parasites (dosed or D-males), or challenged them with infective T. tenuis larvae, to increase parasite intensity (challenged or C-males). We first show that dosing was effective in removing T. tenuis parasites, while parasite intensities increased in challenged birds during the autumn. Because old males initially had more parasites than young males, the treatments generated greater differences in parasite intensity in old than in young males. We also show that various aspects of territorial behaviour (increase in testosterone-dependent comb size in autumn, territorial call rate, likelihood of winning territorial interactions and over-winter survival) were significantly higher in dosed than in challenged males, but in old birds only. Our data thus supported the hypothesis that parasites reduce male aggressiveness during the autumn territorial contests, and could thereby influence recruitment. Our results also highlight that the territorial behaviour of young males, which have fewer parasites, is not as limited by parasites as that of old, previously territorial males. We discuss the implications of these findings for our understanding of the processes regulating red grouse populations and causing their complex, unstable population dynamics.     

Ecology of Nectomys squamipes, the neotropical Water rat, in central Brazil: home range, habitat selection, reproduction and behaviour

Relatively few studies have examined the ecology of small mammals of South American tropical forests. The ecology of the neotropical Water rat, Nectomys squamipes , was investigated in gallery forest in central Brazil during a 14-month mark-recapture study. A total of 11 male and 10 female Water rats were captured; minimum number of animals known alive per month varied from one to four per hectare. Home range size for individuals captured eight or more times was 0.3–1.6 ha. Water rats were captured almost exclusively near the stream or in other inundated portions of the forest. Distance to water, soil moisture, number of tree ferns, number of trees, exposed tree-root cover, and litter cover on the ground were among the variables important in defining microhabitat of N. squamipes. At least some males were in breeding condition (testes scrotal) during all months; females were in breeding condition (vagina perforate) most of the year, but pregnancies were noted only in August, October and November. Captive Water rats consumed plant matter, insects (Blattidae, Gyrinidae, Scarabeidae), tadpoles and small fish. Aquatic prey items were located by searching movements of the forepaws. Water rats demonstrated agility in both climbing and swimming. Physiological dependence of N. squamipes on water is suggested by capture sites and observations of drinking in captive animals.     

Individual voice recognition in a territorial frog (Rana catesbeiana)

Some territorial animals display low levels of aggression towards a familiar territorial neighbour in its usual territory, but exhibit high levels of aggression towards neighbours in novel locations and unfamiliar individuals. Here, we report results from a field playback study that investigated whether territorial males of the North American bullfrog (Rana catesbeiana) could discriminate between the acoustic signals of simulated neighbours and strangers in the absence of contextual cues associated with a specific location. Following repeated exposures to synthetic bullfrog calls from a particular location, subjects responded significantly less aggressively to a familiar call, compared with an unfamiliar one, when both calls were broadcast from familiar and novel locations, indicating that bullfrogs could recognize a neighbour's calls independently of the contextual cues provided by the direction of the neighbour's territory. Subjects responded equally aggressively to unfamiliar calls broadcast from either a familiar or a novel location, which indicates that they could perceive unfamiliar calls as those of a stranger, regardless of where the stranger was encountered. Together, these two results provide evidence that a frog possesses a capacity for individual voice recognition.     

Interpretation of territorial behaviour in terms of a critical disability hypothesis

The hypothesis is that the great majority of behaviour relating to territorial defence presents difficult anomalies in terms of the normal explanatory mechanism of individual selection. Many, if not all, of the difficulties involved can be solved by using a critical disability hypothesis based upon the principle of group selection. Given this latter model, it is possible to predict the development of (1) highly variable territories, (2) microterritories and (3) macroterritories.     

Survival in a long-lived territorial migrant: effects of life-history traits and ecological conditions in wintering and breeding areas

Despite its key role in population dynamics and evolutionary ecology, little is known about factors shaping survival in long‐lived territorial species. Here, we assessed several hypotheses that might explain variability in survival in a migratory Spanish population of a long‐lived territorial species, the Egyptian vulture Neophron percnopterus, using a 16‐year monitoring period and live‐encounter histories of 835 individually marked birds. Cormack‐Jolly‐Seber capture–recapture models showed no evidence for effects of sex or nestling body condition on survival. However, the normalized difference vegetation index (NDVI; an indicator of primary productivity) of natal territories had positive effects on juvenile survival, indicating that environmental conditions experienced early in life can determine survival prospects. Survival increased with age (0.73±0.02 in the first 2 years to 0.78±0.03 in years 3 and 4) to later decrease when birds were five years old (0.60±0.05), the age at which they acquire the adult plumage, abandon the communal lifestyle of juveniles, and may look for a breeding territory. At older ages, survival was higher for non‐breeding (0.75±0.02) and breeding adults (0.83±0.02). Among the latter, birds that recruited into better territories had higher survival prospects. Age‐specific variation in survival in this species may be related to behavioural changes linked to dispersal and recruitment into the breeding population, while survival prospects of adult birds strongly depend on breeding territory selection. These results suggest a tradeoff between recruiting soon, and thus reducing mortality costs of a long and extensive dispersal period, and trying to recruit into a good quality territory. Finally, annual survival rates for birds of all age classes were positively related with the NDVI in their African wintering grounds. Although this relationship was probably mediated by food availability, further research is needed to properly identify the limiting factors that are affecting trans‐Saharan migrants, especially in light of global climate change.     

Breeding behaviour, home range and habitat selection in Rock Firefinches Lagonosticta sanguinodorsalis in the wet and dry season in central Nigeria

Knowledge of a species’ movement behaviour and habitat choice is a prerequisite for assessing its ecological requirements to plan successful conservation strategies. Little is known about these factors in the Rock Firefinch, a recently described species which is probably endemic to the Jos Plateau in central Nigeria. We investigated home range size, habitat use and breeding behaviour of the Rock Firefinch in Amurum forest reserve in central Nigeria during the wet (August–October) and the dry season (November–December) using radiotracking. Birds showed high site fidelity. They mainly moved alone or in pairs but did not have exclusive home ranges. Home range size tended to be larger during the dry season due to long movements to water sources. Birds generally preferred inselberg habitat and avoided farmland. During the dry season they additionally utilized gallery forests where water was readily available, and as a result of having to cross scrub savannah to get to water, scrub savannah was also more heavily used during the dry season. Birds bred between the late rainy (September–October) and the early dry season (November). Nest‐sites were associated with rocky boulders. Both sexes contributed to incubation. Daily egg survival rate calculated using the Mayfield method was 0.89 (0.83–0.95 95% confidence interval); no nests failed during the chick stage, but sample size was only four nests. Of all 14 nests found, 50% were depredated and only 29% of breeding attempts succeeded in producing Rock Firefinch chicks. A second breeding attempt was recorded when the first one failed. Chick production just about compensated adult mortality (measured in a separate study at the site) such that the population is probably stable at present. However, given the large uncertainty in our underlying assumptions, more data are needed to confirm this. We suggest that the presence of inselberg habitat in close proximity to water sources is the essential and limiting resource for this species.     

The role of testosterone in male downy woodpeckers in winter home range use, mate interactions and female foraging behaviour

Studies of the role of testosterone (T) in birds have typically focused on sexual or aggressive behaviours of males during the breeding period, but males of nonmigratory species may invest in mate and territory long before breeding, and the influence of T in facilitating nonbreeding-season behaviours is poorly understood. We gave free-living male downy woodpeckers, Picoides pubescens, T-implants during the winter to determine whether elevated levels of T increased a male's ability to exclusively occupy territory-based resources, and whether elevated T strengthened a male's investment in an existing pair bond relationship. We also explored how a female's foraging efficiency might be affected by her mate's behaviour if he had elevated T. We found little difference between control and T-implanted males with regard to home range exclusivity. Surprisingly, male-male display rates were significantly lower in T-implanted males than in controls. Regarding male-female interactions, T-implanted males that experienced high incursion rates from other males maintained more frequent spatial association with their mate, suggesting that T facilitates male behaviours that could restrict the mate's access to other male birds. Female mates of T-males showed reduced foraging rates, but because male-female aggression was similar between treatment groups, the cause for this reduction is unknown. The results indicate that exogenous T during winter affects a variety of behaviours in male woodpeckers, and proximate influences on pair bond maintenance in winter may be a fruitful avenue for future research.     

Juvenile dispersal behaviour and natal philopatry of a long-lived raptor, the Spanish Imperial Eagle Aquila adalberti

The dispersal behaviour of 30 radio-tagged young Spanish Imperial Eagles Aquila adalberti was studied in southwestern Spain in 1986–1990. The dispersal process involved first departure from the natal population, exploratory movements, temporary settlements and returns to the natal population. The dispersal process lasted for the whole of the immature period studied, and behaviour was radically different from that displayed by territorial adults. Movements between temporary settling areas and the natal population occurred continually throughout the dispersal period. Return to the natal population could be used by the young to explore the possibilities for pair formation where a vacancy may have occurred in the breeding population.     

Influence of a novel object in the home range of the cockroach,Blattella germanica

We investigated whether exploratory behaviour of the cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae), was modified by the introduction of a novel object, such as a bait station, into their familiar home range. In particular, we measured the attractiveness of boxes, as novel objects, in relation to their complexity and to their contents. The presence of a novel object induced an increase of exploratory behaviour on and inside the object and its environs. Time spent around the object depended on the complexity of the object (closed box or with holes). The more complex the object, the longer cockroaches spent exploring it. When the object contained food, its attractiveness was greatly increased and it affected cockroaches from further away.