Comparative studies on vertical separation,foraging behavior and traveling mode of saddle-backed tamarins (Saguinus fuscicollis) and red-chested moustached tamarins (Saguinus labiatus) in Northern Bolivia

The author made comparative studies on the ecology of saddle-backed tamarins (Saguinus fuscicollis) and red-chested moustached tamarins (S. labiatus) on the upper Amazon in northern Bolivia. The unit group of both species of monkeys was a family group composed of two to seven individuals, but they often formed polyspecific associations comprising one such family group each. However, both species preferred different layers of forest for foraging insects and traveling.S. fuscicollis mainly utilized the lower layer of the forest and foraged large-sized insects lurking in tree hollows, whereasS. labiatus mainly utilized the middle layer of the forest and foraged small-sized animals on branches. These differences were more clearly noticeable in secondary forest than in primary forest.     

Troop-specific responses to long calls of isolated tamarins (Saguinus mystax)

Recently captured moustached tamarins (Saguinus mystax) were briefly separated from other members of their troop. Most separated animals emitted long calls that were, in general, similar in acoustic structure to those of sympatric tamarin species while retaining species distinctiveness. Individual differences also appeared in call structure. The long calls of a separated animal were responded to almost entirely by members of the animal's own troop rather than by other troops, and reciprocal calling occurred among troop members significantly more often than expected by chance. Although there was no evidence of troop-specific call structure or dialect, there were troop-specific responses to the calls of separated tamarins. This response implies the existence of a stable and integrated troop structure that allows troop members to learn and to respond to the individual specific features of each troop member's calls.     

The response of adult orang-utans to flanged male long calls: inferences about their function

Flanged male orang-utans emit loud vocalizations called long calls. In this study, we examined the correlates of variation in long-calling rates among flanged male Sumatran orang-utans, as well as the ranging responses of adult females and flanged males to these long calls. Males that gave calls more often were more likely to approach calls by others. Results bolster a female attraction function of long calls. Flanged males did not significantly avoid or approach long calls. However, males called more when alone than when guarding a female mate, and adult females significantly approached long calls, especially those of the dominant male, and did so regardless of their reproductive state, allowing them to remain within earshot of calling males. The possible selective advantages of this response include avoidance of harassment and infanticide by males. These findings confirm the existence of some form of social organization above the mother-infant unit.     

Acoustic differences between spontaneous and induced long calls of golden lion tamarins,Leontopithecus rosalia

Long calls are emitted by several primate taxa and appear to have multiple functions related to spacing mechanisms and reproduction. Yet, in some species the spontaneous rate of emission of these calls is low, and playbacks are used to elicit long calls to augment the sample size of studies. The objective of this study was to compare the acoustic structure of spontaneously emitted and experimentally induced long calls of golden lion tamarins. Results from 6 adult tamarins show that spontaneously emitted long calls differ acoustically from experimentally induced long calls in several frequency measures. Several explanations for these differences are discussed. We conclude that regardless of the underlying mechanisms, playbacks elicit responses that may be different from naturally occurring calls.     

Dentition of moustached tamarins (Saguinus mystax mystax) from Padre Isla, Peru, part 1: quantitative variation

Analyses of dental variation in geographically restricted, wild populations of primates are extremely rare; however, such data form the best source for models of likely degrees of variation within and between fossil species. Data from dental casts of a geographically restricted population of moustached tamarins (Saguinus mystax mystax) from Padre Isla, Peru, document high levels of dental variability, as measured by coefficients of variation, in a nonsexually dimorphic species, despite its isolation and small population size. Like other primates, moustached tamarins show lower variability in the dimensions of the first molars and increased variability in the dimensions of the final molars in the toothrow. Moustached tamarins from Padre Isla have a distinctive pattern of variability in the remaining teeth, including more stable tooth lengths in the anterior and posterior portions of the toothrow, and more stable tooth widths in the midregion of the toothrow. High variability in incisor width may be due to age effects of a distinctive diet and pattern of dental wear.     

The units of perception in the antiphonal calling behavior of cotton-top tamarins (Saguinus oedipus): playback experiments with long calls

We investigated how the acoustic structure of the cotton-top tamarin monkey's (Saguinus oedipus) combination long call relates to the antiphonal calling behavior of conspecifics. Combination long calls can function as contact calls and are produced by socially isolated individuals. Often conspecifics respond to these calls with their own long calls. Structurally, these calls are always composed of one or more 'chirps' followed by two or more 'whistles'. We compared the antiphonal calling responses to playbacks of complete, naturally produced long calls versus single whistles or single chirps. Subjects responded significantly more to whole calls than to either syllable-type alone. Thus, our data suggest that, in terms of the antiphonal calling behavior of socially isolated conspecifics, the whole long call is the unit of perception.     

Learning fine-tunes a specific response of nestlings to the parental alarm calls of their own species

Parent birds often give alarm calls when a predator approaches their nest. However, it is not clear whether these alarms function to warn nestlings, nor is it known whether nestling responses are species-specific. The parental alarms of reed warblers, Acrocephalus scirpaceus ("churr"), dunnocks, Prunella modularis ("tseep"), and robins, Erithacus rubecula ("seee") are very different. Playback experiments revealed that nestlings of all three species ceased begging only in response to conspecific alarm calls. These differences between species in response are not simply a product of differences in raising environment, because when newly hatched dunnocks and robins were cross-fostered to nests of the other two species, they did not develop a response to their foster species' alarms. Instead, they still responded specifically to their own species' alarms. However, their response was less strong than that of nestlings raised normally by their own species. We suggest that, as in song development, a neural template enables nestlings to recognize features of their own species' signals from a background of irrelevant sounds, but learning then fine-tunes the response to reduce recognition errors.     

Synthetic bird calls and their application to scaring methods

This paper suggests means of synthesizing efficient signals for bird scaring and examines five ways in which synthetic signals may be more efficient: the coding/decoding process, transmission through the environment, interspecificity, habituation and broadcasting techniques. Examples are taken from our own studies comparing natural and synthetic distress calls.     

The response of bird populations to habitat loss

Environmental change through altered climate and land use could have a severe impact on bird populations. Predicting the consequences for the size of bird populations is one of the crucial problems for their conservation. We show how a population model based on the behaviour of individuals can be used to predict the consequences of habitat loss. For a wide range of conditions, loss of either wintering or breeding habitat results in population reduction. The approach is then extended to consider the impact of habitat loss in the wintering area on bird species with complex migratory systems. This shows that 'knock-on' effects may occur, so that habitat loss in a wintering area may affect populations which did not initially use that area. The ability to alter migration routes in response to environmental change may be crucial to the future viability of populations. Using a simple model combining genetics and population dynamics, we show that aspects of the biology of a species may affect whether or not its migration strategy is flexible enough to shift in response to habitat change. Some species may be able to adopt new migration routes and avoid the catastrophic consequences of habitat loss in traditional wintering areas; however, other species may lack this flexibility and may suffer severe population declines as a consequence.     

Incoming solar radiation patterns and vegetation response: Examples from the natal drakensberg

Summary A method of accurately estimating and mapping patterns of incoming solar radiation fluxes on sloping terrain, using data from standard meteorological instruments, is described. The results of the radiation maps produced are then related to a specific example of vegetation successional changes in the Cathedral Peak area of the Natal Drakensberg mountain range, indicating that these changes occur most readily on cooler aspects. For the same region, the differences in the major plant communities at two other sites, attributable largely to variations in incoming solar radiation loads, are discussed.The authors wish to thank the Department of Forestry of the Republic of South Africa for providing data and for facilitating fieldwork to be undertaken at Cathedral Peak. This Research was funded in part by the South African Council for Scientific and Industrial Research, whose support is hereby gratefully acknowledged (by R.E.S.). The maps illustrating this paper were prepared by Mrs. C. Coetzee and Mr B. Martin of the University of Natal, Pietermaritzburg.     

Genetic structure and functioning of alien ship rat populations from a Corsican micro-insular complex

The detrimental effects of the introduced ship rat on bird species on the Lavezzi Mediterranean archipelago has led to the decision to eradicate the rodent from the main island, Lavezzu (73 ha), as well as from several neighbouring islets. A genetic study using eight microsatellite markers has revealed some of the dynamics of this rat population. First, it has been shown that the rat population was genetically stable (no departure from Hardy-Weinberg equilibrium and no linkage disequilibrium) and as suggested by paleontological data, established for a long time. This information is encouraging in term of viability of the eradication campaign in the long term, even if rare immigration events cannot be excluded. Second, this study shows that rats are likely to swim between the main island and the islets quite regularly since no clear genetic differentiation has been detected between them. This result is quite surprising since the ship rat is not known for its swimming abilities. Third, a cryptic genetic structure has been detected on the main island, with the north peninsula differentiated from the rest. This result correlates the observation of particular predation behaviours only observed in this part of the island. Finally, evolutionary hypotheses (e.g., dispersal limitation, emergence of family groups, local adaptation) are discussed to explain the genetic patterns observed and the population functioning inferred. These results should be of particular interest to wildlife managers concerned with rat eradications, and also provide clear insights into the study of other biological invasions.     

Combining tactics to exploit Allee effects for eradication of alien insect populations

Invasive species increasingly threaten ecosystems, food production, and human welfare worldwide. Hundreds of eradication programs have targeted a wide range of nonnative insect species to mitigate the economic and ecological impacts of biological invasions. Many such programs used multiple tactics to achieve this goal, but interactions between tactics have received little formal consideration, specifically as they interact with Allee dynamics. If a population can be driven below an Allee threshold, extinction becomes more probable because of factors such as the failure to find mates, satiate natural enemies, or successfully exploit food resources, as well as demographic and environmental stochasticity. A key implication of an Allee threshold is that the population can be eradicated without the need and expense of killing the last individuals. Some combinations of control tactics could interact with Allee dynamics to increase the probability of successful eradication. Combinations of tactics can be considered to have synergistic (greater efficiency in achieving extinction from the combination), additive (no improvement over single tactics alone), or antagonistic (reduced efficiency from the combination) effects on Allee dynamics. We highlight examples of combinations of tactics likely to act synergistically, additively, or antagonistically on pest populations. By exploiting the interacting effects of multiple tactics on Allee dynamics, the success and cost-effectiveness of eradication programs can be enhanced.     

From nestling calls to fledgling silence: adaptive timing of change in response to aerial alarm calls

Young birds and mammals are extremely vulnerable to predators and so should benefit from responding to parental alarm calls warning of danger. However, young often respond differently from adults. This difference may reflect: (i) an imperfect stage in the gradual development of adult behaviour or (ii) an adaptation to different vulnerability. Altricial birds provide an excellent model to test for adaptive changes with age in response to alarm calls, because fledglings are vulnerable to a different range of predators than nestlings. For example, a flying hawk is irrelevant to a nestling in a enclosed nest, but is dangerous to that individual once it has left the nest, so we predict that young develop a response to aerial alarm calls to coincide with fledging. Supporting our prediction, recently fledged white-browed scrubwrens, Sericornis frontalis, fell silent immediately after playback of their parents' aerial alarm call, whereas nestlings continued to calling despite hearing the playback. Young scrubwrens are therefore exquisitely adapted to the changing risks faced during development.     

Diet and feeding ecology of saddle-back (Saguinus fuscicollis) and moustached (S. mystax) tamarins in an Amazonian terra firme forest

The feeding ecology of two small-bodied primate species—saddle-back ( Saguinus fuscicollis auilapiresi ) and moustached tamarins ( S. mystax pileatus )—occurring in stable, mixed-species groups was studied in a terra firme forest site in the upper Urucu River, Amazonas, Brazil. Ecological data are based primarily on one mixed-species group of 5–8 saddle-back and 8–10 moustached tamarins. The overall vegetative and animal-prey components of each tamarin species' diet, their selection of food species, and the seasonal variation in their use of plant resources are described, and compared to those of callitrichids elsewhere. The extremely diverse diet of tamarins included at least 136 tree, 33 vine and liana, 12 epiphyte and nine shrub species, as well as a wide range of prey items. They fed primarily on ripe fruit pulp of most of these species for most of the year, but shifted to floral nectar and plant exudates of a few key plant species during the dry season. Taxonomic overlap in plant diet was nearly complete between the two tamarin species, but they diverged considerably in their prey capture techniques. Saddle-backs used the low forest understorey, and manipulatively searched for sedentary prey concealed within discrete, usually rigid, microhabitats, whereas moustached tamarins used the midstorey where they visually searched for mobile prey well exposed on foliage. These and other feeding and foraging patterns are discussed in the light of other callitrichid species studied to date.     

哺乳期棕色田鼠对非亲缘幼仔的行为反应

通过观察产后2 日(L2)、6 日(L6)、10 日(L10)、14 日(L14)和20 日(L20)的棕色田鼠母鼠对2 日龄、6 日龄、10 日龄和14 日龄非亲缘幼仔的攻击行为和衔回行为,探讨了哺乳期棕色田鼠的母性行为与非亲缘幼仔的发育(日龄或个体大小)及母鼠产后时间的关系。结果表明,在哺乳前期(L2,L6),非亲缘幼仔的日龄大小显著影响母鼠的攻击行为(P < 0.05);在哺乳中期(L10,L14)及后期(L20),非亲缘幼仔的日龄对母鼠的攻击行为没有显著影响(P > 0. 05)。在整个哺乳期,母鼠对14 日龄非亲缘幼仔的攻击频次最高(P < 0.05)。产后不同时间的母鼠对同一日龄非亲缘幼仔的攻击频次没有显著差异(P > 0.05)。这些结果表明,哺乳期内的棕色田鼠对非亲缘幼仔的攻击与幼仔的发育有关,与母鼠的产后时间无关。     

Lacustrine sockeye salmon return straight to their natal area from open water using both visual and olfactory cues

Mechanisms of the amazing ability of salmon to migrate a long distance from open water to natal streams for spawning are still unknown. Lacustrine sockeye salmon (Oncorhynchus nerka) in Lake Toya offers an excellent model system for studying the orientation mechanism in open water, because mature fish return to the natal area with a high degree of accuracy. First we examined the percentage of fish returning to the natal area after they were released 7 km south of the natal area. Forty percent of control male mature fish and 25% of the fish blinded by injection of a mixture of carbon toner and corn oil into the eyeball were captured in the natal area within 5 days. Forty-four percent of fish with brass rings (control) and 31% of fish with NdFe magnetic rings which interfere with the magnetic cue were captured in the natal area within 3 days. These experiments suggested that, although the number of blinded fish captured in the natal area was less than that of the controls, the difference was not statistically significant. In the fish captured in the natal area within 3 or 5 days, fish which found the natal area using their olfactory cue after random swimming for a long time and returned to that area may be included. Hence we tracked fish telemetrically using an ultrasonic tracking system, and found that mature males released at a long distance (3.6 or 6.8 km) from the natal area swam straight to the vicinity of the natal area. Interference of the magnetic cue by the attachment of a magnetic ring did not affect their direct return. Blockage of the visual cue caused them to move randomly. These data suggest that lacustrine sockeye salmon return straight to the vicinity of the natal area using their visual cue and finally reach the exact homing point using their olfactory cue.