Modeling the impact of feeding stations on vulture scavenging service efficiency

Vultures, the only vertebrate obligate scavengers, are currently facing a dramatic worldwide decline with over half of vulture species now classified as threatened. To address this widespread decline, the use of feeding stations has been widely advocated in recovery programs. However, providing food that is more predictable in time and space than natural resources could disrupt the ecological scavenging service provided by vultures. In this study, we build a multi-agent system (MAS), which describes the social foraging behavior of Gyps vultures in order to investigate how resource predictability in space and resource management affect scavenging service efficiency. We study the possibility that vultures take into account feeding station location in addition of using local enhancement. Our results show that the efficiency of the scavenging service is heavily affected by the way resources are distributed between feeding stations and natural areas. Nevertheless, it appears possible to minimize a loss in service efficiency by increasing the number of feeding stations while keeping the total amount of resources available constant, thus reducing the predictability of the resources located on the stations. We illustrate our work in the case of European feeding stations that provide supplementary resources in areas where natural ones are scarce. Moreover, we discuss the implications worldwide, in particular in the case of India, where feeding stations for vultures are intended to lure individuals away from potentially harmful natural carrion.     

Individual experience-based foraging can generate community territorial structure for competing ant species

To gain additional territory while defending existing territory, animals must acquire and use information regarding resource characteristics and competitive pressure. For social organisms like ants, individual workers have experiences to acquire information, but territory establishment is a colony level behavior. Colony behavior, in turn, affects community structure. Here, I investigate how an individual ant’s previous experience affects its future foraging behavior and how individual behaviors can scale up to community territorial structure for two coexisting Formica species. To do this, I combine a field survey, a multi-agent computer simulation, and a manipulation experiment. The field survey shows that workers of both species co-occur on many trees early in the season, but ants on trees become segregated by species as the season progresses. The simulation demonstrates how this segregated spatial distribution can result from ants using a foraging strategy in which individuals show a preference for foraging sites based on previous experience. The experiment suggests that these ants are indeed capable of experience-based foraging behavior; ants preferentially return to sites where they have had positive experiences and avoid sites where they have had negative experiences. Results from this study suggest that spatially explicit information can be collected and stored by individuals to facilitate colony territorial structure, and that future investigations of community territory formation should include effects of individual previous experience.     

The dynamics of social learning in an insect model,the bumblebee (<Emphasis Type="Italic">Bombus terrestris</Emphasis>)

Bumblebees (Bombus terrestris) are attracted to those particular inflorescences where other bees are already foraging, a process known as local enhancement. Here, we use a quantitative analysis of learning in a foraging task to illustrate that this attraction can lead bees to learn more quickly which flower species are rewarding if they forage in the company of experienced conspecifics. This effect can also be elicited by model bees, rather than live demonstrators. We also show that local enhancement in bumblebees most likely reflects a general attraction to conspecifics that is not limited to a foraging context. Based on the widespread occurrence of both local enhancement and associative learning in the invertebrates, we suggest that social influences on learning in this group may be more common than the current literature would suggest and that invertebrates may provide a useful model for understanding how learning processes based on social information evolve.     

Directional change in a suite of foraging behaviors in tropical and temperate evolved honey bees (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.)

The concept of a suite of foraging behaviors was introduced as a set of traits showing associative directional change as a characterization of adaptive evolution. I report how naturally selected differential sucrose response thresholds directionally affected a suite of honey bee foraging behaviors. Africanized and European honey bees were tested for their proboscis extension response thresholds to ascending sucrose concentrations, reared in common European colonies and, captured returning from their earliest observed foraging flight. Race constrained sucrose response threshold such that Africanized bees had significantly lower sucrose response thresholds. A Cox proportional hazards regression model of honey bee race and sucrose response threshold indicated that Africanized bees were 29% (P<0.01) more at risk to forage over the 30-day experimental period. Sucrose response threshold organized age of first foraging such that each unit decrease in sucrose response threshold increased risk to forage by 14.3% (P<0.0001). Africanized bees were more likely to return as pollen and water foragers than European foragers. Africanized foragers returned with nectar that was significantly less concentrated than European foragers. A comparative analysis of artificial and naturally selected populations with differential sucrose response thresholds and the common suite of directional change in foraging behaviors is discussed. A suite of foraging behaviors changed with a change in sucrose response threshold that appeared as a product of functional ecological adaptation.Communicated by R.F.A. Moritz     

Regulation of pollen foraging in honeybee colonies: effects of young brood, stored pollen, and empty space

Pollen storage in a colony of Apis mellifera is actively regulated by increasing and decreasing pollen foraging according to the “colony's needs.” It has been shown that nectar foragers indirectly gather information about the nectar supply of the colony from nestmates without estimating the amount of honey actually stored in the combs. Very little is known about how the actual colony need is perceived with respect to pollen foraging. Two factors influence the need for pollen: the quantity of pollen stored in cells and the amount of brood. To elucidate the mechanisms of perception, we changed the environment within normal-sized colonies by adding pollen or young brood and measured the pollen-foraging activity, while foragers had either direct access to them or not. Our results show that the amount of stored pollen, young brood, and empty space directly provide important stimuli that affect foraging behavior. Different mechanisms for forager perception of the change in the environment are discussed. Received: 13 June 1998 / Accepted after revision: 25 October 1998     

The Value of Rehabilitating Logged Rainforest for Birds

Abstract: The recent advent of carbon crediting has led to a rapid rise in biosequestration projects that seek to remove carbon from the atmosphere through afforestation and forest rehabilitation. Such projects also present an important potential opportunity to reverse biodiversity losses resulting from deforestation and forest degradation, but the biodiversity benefits of different forms of biosequestration have not been considered adequately. We captured birds in mist nets to examine the effects of rehabilitation of logged forest on birds in Sabah, Borneo, and to test the hypothesis that rehabilitation restores avian assemblages within regenerating forest to a condition closer to that seen in unlogged forest. Species richness and diversity were similar in unlogged and rehabilitated forest, but significantly lower in naturally regenerating forest. Rehabilitation resulted in a relatively rapid recovery of populations of insectivores within logged forest, especially those species that forage by sallying, but had a marked adverse effect on frugivores and possibly reduced the overall abundance of birds within regenerating forest. In view of these results, we advocate increased management for heterogeneity within rehabilitated forests, but we strongly urge an increased role for forest rehabilitation in the design and implementation of a biodiversity‐friendly carbon‐offsetting market.     

Kin recognition in the common lizard

The ability to recognize parents has never been reported in species in which parents do not provide care to their young; in such species, only sibling recognition has been found. However, there may be several advantages of parent recognition, even in the absence of parental care. We investigated the ability of neonates to recognize olfactory cues from both their mother and siblings in the common lizard, Lacerta vivipara, a species without parental care. Juveniles from 264 gravid females were reared for 2 days either with their mother, with another female, or separated from all other adults. Juveniles from some families were split into two or three groups so that each juvenile was unfamiliar with a subset of its siblings. After 2 days, we offered the juveniles a choice of two nocturnal shelters: one containing a lizard odor and the other without odor. The response to the odor of an unrelated and unfamiliar adult was influenced by both the sex of the adult and the sex of the juvenile. Juveniles of both sexes recognized the odor of their mother whether they were familiar with her or not (pre-natal determinism). Juveniles recognized familiar but not unfamiliar siblings (post-natal determinism). In the wild, spatial association with kin declines shortly after birth. Thus, recognition of the mother is likely to have biological relevance. Recognition of the mother may reduce competition and/or enhance juvenile establishment. Received: 15 May 1997 / Accepted after revision: 29 December 1997     

Social foraging in stingless bees: how colonies of Melipona fasciata choose among nectar sources

In an experimental set-up, a colony of the stingless bee Melipona fasciata demonstrated its ability to choose the better of two nectar sources. This colony pattern was a result of the following individual behavioural decisions: continue foraging, abandon the feeder, restart foraging and initiate foraging. Only very rarely did individuals switch from one feeder to the other. With the first combination of a rich (2.7 M) and a poor (0.8 M) feeder M. fasciata behaved differently from Apis mellifera. Recruitment occurred to both feeders and the poor feeder was not abandoned completely. When the poor feeder was set to 0.4 M, M. fasciata abandoned the poor feeder rapidly and allocated more foragers to the rich feeder. These patterns were similar to those reported for A. mellifera with the first combination of feeders. Over a sequence of 4 days, experienced bees increasingly determined the colony patterns, and the major function of communication between workers became the reactivation of experienced foragers. The foragers modulated their behaviour not only according to the profitability of the feeder, but also according to previous experience with profitability switches. Thus, experience and communication together regulated colony foraging behaviour. These findings and the results of studies with honeybees suggest that M. fasciata and honeybees use similar decision-making mechanisms and only partly different tools. Received: 21 December 1998 / Accepted: 5 January 1999     

Studying Trophic Relationships of the Bee Seladonia subaurata (Rossi) (Hymenoptera,Halictidae) by Analyzing Pollen from Nest Cells

Abstract–Pollen of 42 plant species from 17 families has been found in the food stores of Seladonia subaurata nests, with 61–86% of the pollen being accounted for by the Compositae. The foragers are characterized by strict flower preferences: more than 90% of the pollen in each cell belongs to two or three, sometimes four, plant species. At the eusocial stage of the existence of a colony, two or three foragers usually provision each cell. In especially large colonies, foragers are divided into groups and provision several cells during the day.     

A model for the evolution of communal foraging in hierarchically structured populations

A kin selection model is described for populations in which groups of interacting individuals (trait groups, sensu Wilson 1975) are spatially situated within larger aggregations. The model predicts the optimal foraging strategy when resources are shared with other trait group members and there is an individual risk in foraging. The ecological mechanism of variation in group fitness, differential resource accumulation, is explicitly incorporated into the model. The optimal foraging rate obtained from this model depends on the product of a benefit-to-cost ratio and a relatedness parameter. The appropriate definition of relatedness for the evolution of communal foraging is determined by the details of the ecological interaction between consumers and resources. When competition is purely intra-specific, the genetic correlation among interactants relative to other members of the local aggregation defines the relatedness parameter applicable to selection on foraging propensity. When competition is primarily inter-specific, the genetic correlation among trait group members relative to the entire population defines relatedness.