Foraging Style Research Articles

Foraging activity and night-roost usage in the Japanese greater horseshoe bat, Rhinolophus ferrumequinum nippon

Nocturnal activity, foraging behavior and night-roost usage in Rhinolophus ferrumequinum nippon were examined using bat-detectors, radio transmitters and fluorescent tags. Emergence from the cave roost began around dusk from March to November. The mean emergence time averaged 14 min after sunset, and the principal foraging period was within a few hours after sunset. The main foraging style was flycatching (perch-hunting). The height of the branches used by bats as feeding or roosting sites averaged 4.1 m above the ground. The length of bat's stay per feeding site averaged 6.6 min. In June, August and September, once the bats emerged, they seldom returned to the cave until just before sunrise, but in July, lactating females returned to the cave before midnight. In November, most of the bats returned to the cave about two hrs after sunset. Home range of adult females averaged 1.5 ha, and they foraged mainly in open forests, woodland paths or forest edges. The distances traveled to their main foraging sites averaged 0.87 km. Maximum-recorded distance traveled was 2.3 km during one night, and they hunted up to a distance of 2.0 km from the cave. Bats used specific night roosts, and their roosting bouts in the night roosts extended for about six hrs in April and varied from one to five hrs in June and October.

Patagial complex evolution in hummingbirds and swifts (Apodiformes): a molecular phylogenetic perspective

Studies of the role of flight in vertebrate evolution often have focused on the propatagial muscle complex because this structure forms the wing's leading edge. However, historical narratives about the evolution of flight anatomy are compromised because traditional higher-level taxonomies typically are based in part on the propatagium itself. To avoid this circularity, I used a consensus molecular phylogeny to examine propatagial evolution in the highly aerial sister groups, hummingbirds and swifts (Apodiformes). Mapping of anatomy on molecular-based phylogeny indicates that structural variation in M. tensor propatagialis pars brevis (TPB) is congruent with the major subclades of both hummingbirds and swifts. However, the humeral tendon and broad attachment of the fleshy belly of TPB with M. extensor metacarpi radialis (EMR) most likely underwent parallel change in hummingbirds and swifts, while the distal tendon present only in hummingbirds changed from a thin sheet to a strong tendon. The combination of divergent (within hummingbirds or swifts) and parallel (between hummingbirds and swifts) evolutionary patterns implies that the taxonomic value of the propatagial complex in apodiformes depends on anatomical component and level of divergence. The congruence of anatomy with molecular phylogeny provides independent criteria for designating relatively ancestral versus derived clades of apodiformes. Based on these polarities, living hummingbirds and swifts express additional parallel trends from arboreal to more aerial foraging styles, and from depauperate to species-rich clades. Within apodiformes, the link of flight anatomy with taxonomic and ecologic diversity suggests that elaboration of locomotor modes was important for apodiform diversification, echoing a similar pattern for birds relative to their reptilian ancestors.

Responses of Captive Single- and Mixed-Species Groups of Saguinus to Novel Nonthreatening Objects

The provision of novel objects allows one to probe for behavioural differences among species. This is particularly relevant when studying species that form mixed-species groups, as divergent responses may provide clues to the advantages that individuals gain from associating. We compared the responsiveness to novel objects in captive single- and mixed-species groups of saddleback (Saguinus fuscicollis) and red-bellied (Saguinus labiatus) tamarins to determine the influence of a congener. We tested groups with novel objects placed near the top, the middle, and on the floor of their enclosures and measured latency to approach and touch them. We tested predictions related to differences in lifestyle patterns under natural conditions. As we predicted, S.labiatus, which usually occur at a higher mean height in the forest than their congeners, responded to objects placed near the top of the enclosure significantly quicker in both single- and mixed-species groups. S. fuscicollis responded to objects placed on the floor quicker, and in mixed-species groups S. fuscicollis approached them before S. labiatus did. There were specific differences in median touch–approach time (T-A): Saguinus fuscicollis had a shorter T-A time than that of S. labiatus, which can be related to their manipulative foraging style. Reaction times decreased in mixed-species trials for both species, suggesting that the reaction of one species may effect the congener. Both species may benefit through association, though the dominance of Saguinus labiatus over S. fuscicollis may limit the advantages to S. fuscicollis. Over all our study supports the idea that cross-specific social facilitation is an important consequence of mixed-species groups of Saguinus.

Distribution of the Spotted Bat, Euderma maculatum, in California

There were 14 records, including the type, for Euderma maculatum in California between 1891–1991. All involved salvage of single bats; most indviduals were dead or moribund. In surveys from 1992 to 1997, using primarily acoustic sampling at possible foraging sites within a few kilometers of fractured resistant rock cliffs, 23 additional localities were identified, including a range extension into the Klamath Mountains of northwestern California. E. maculatum typically was encountered foraging in meadows on the edge of forests in mixed conifer-hardwood habitat at elevations of 800–1,500 m, but observations extend to 2,926 m in the Sierra Nevada. Usually one E. maculatum was observed at a foraging site, but occasionally two or three were present simultaneously. These records suggest that the species, while typically at low density within a few kilometers of geomorphically defined roosts, occurs more widely than previously realized. Although its foraging style and characteristics of its call are distinctive, E. maculatum overlaps extensively both in geographic range and use of roosts in rock cliffs with several other species of bat, notably Eumops perotis, which also has an audible echolocation call. The linked pattern of rarity, patchy distribution, and restrictive roosting requirements place this species at risk.

Community structure and evolution of insectivorous bats in the Palaeotropics and Neotropics

ABSTRACTThe most diverse known communities of insectivorous bats in the Palaeotropics and Neotropics are similar in alpha diversity (number of species). However, they show distinct differences with respect to wing morphology and the echolocation behaviour of their component species. In the Palaeotropics, most bat families are clearly separated in wing morphospace. The morphological niche of Rhinolophidae is vacant in the Neotropics, but primitive echolocators using sound primarily for scanning the environment rather than for prey capture are much more frequent there than in the Palaeotropics. In our opinion, a large portion of this difference can be traced to the different evolutionary histories of the respective communities. Bat families of different geographical origin are involved and their foraging styles obviously evolved differently in the Old and New World.

Sit-And-Wait Predators and Cryptic Prey: A Field Study with Wild Birds

(1) I recorded the ability of ten colour ringed robins Erithacus rubecula and nine great tits Parus major to detect immobile, cryptic prey in the wild. Artificial prey were presented at high density on horizontal backgrounds at ground level (experiment 1). Another type of artificial prey was presented at low density above ground on bark (experiment 2). The prey were either 'cryptic' or 'conspicuous'. (2) In experiment 1, five robins simply fed faster on the conspicuous food-there was no evidence that the robins acquired 'search images' during repeated feeding bouts on cryptic prey. (3) Only two great tits and a robin out of the seventeen birds that started experiment 2 learnt how to detect cryptic 'Puffa-puffa' rice prey. The juvenile robin used a 'sit-and-wait' style of foraging which allowed it to sight over half the cryptic prey as quickly as it took to scan for conspicuous prey. However, the remaining cryptic prey were preceded by abnormally long 'search times'; the robin also made unsuccessful visits to the background which were followed by pecks to the bark instead of prey. (4) The two great tits also showed an intermittent ability to detect the cryptic prey; if they failed to sight the prey from long distance (which occurred in over three-quarters of their visits), they resorted to an energy and time consuming 'continuous' foraging style on the bark. (5) Thus the ability to detect cryptic prey from vantage points without relying on movement as a cue, was restricted to only a few birds (of those filmed). Without extensive experience these birds could not learn to deal efficiently with cryptic prey.

Foraging Behavior of Competing Africanized Honeybees and Stingless Bees

The colonizing success and potential influence of immigrant Africanized honeybees in the neotropics depends on their foraging style and competitive ability. Experiments were performed to compare the foraging tactics of this invading species to those of its most abundant competitors, highly social stingless bees of the genera Melipona and Trigona. In an area containing a rich assemblage of stingless bees in French Guiana, Africanized honeybees were significantly more abundant on honey—water feeders during a high "nectar flow" period than combined stingless bee and wasp species. During the last 15 min of the experiments, when bait was not replenished on feeders, Africanized honeybees abandoned the feeders but native foragers continued to arrive. None of the stingless bees, including four aggressive Trigona, displaced from the feeders the foragers of several (two to seven) colonies of Africanized honeybees. The cost of attacking Africanized honeybees at feeders apparently exceeded the benefit for large, aggressive Trigona williana and T. hyalinata branneri. These bees abandoned feeders visited by nonaggressive Africanized honeybees. Single, small Africanized honeybee colonies were displaced from feeders by aggressive foragers of T. Pallens pallens and T. h. branneri. In one instance Africanized honeybeeys shifted almost immediately to a floral resource, while abandonment of the feeders by T. williana was not followed by a shift to a natural food source. Reduction of competitive interaction with Africanized honeybees was accomplished by foragers of T. clavipes and T. p. pallens that partitioned four feeders by visiting only two, leaving the other to Africanized bees. Interspecific displacement was never absolute; a few foragers from a displaced colony always visited the feeders. Africanized honeybees and Melipona fulva foraged nonaggressively both at feeders and flowers, but Africanized bees at feeders exhibited low levels of aggression toward Melipona and polybiine wasps on one occasion. Unlike other aggressive Trigona, T. clavipes was at times unaggressive. Colonies of T. h. branneri and Africanized honeybees, the bees most successful in displacing other species from feeders, were comprised of many more workers than colonies of the other bees. The combined advantages of (1) the ability to communicate the distance and direction of a food source from the nest, (2) large forager size, and (3) large colony size provide Africanized honeybee colonies with a competitive ability superior to that of stingless bees at rich, compact resources.