Intraspecific differences in benefits from feeding in mixed-species flocks

The Madagascar Paradise Flycatcher Terpsiphone mutata and Common Newtonia Newtonia brunneicauda frequently form two-species flocks in the deciduous dry forest of western Madagascar. In T. mutata , some males have long tails, while other males and females have short tails. When foraging in mixed flocks, each type of bird captured prey more rapidly than otherwise, but the degree of increase in feeding rate was smaller in long-tailed males. When in mixed flocks, all T. mutata caught prey on leaves in the canopy where N. brunneicauda foraged. Long-tailed males changed feeding habits from sallying when not in mixed flocks, whereas short-tailed birds showed no change of feeding habit. The elongated tails of long-tailed males may have made their foraging less efficient owing to decreased agility in the canopy. N. brunneicauda is monomorphic and often formed groups of three to five individuals. In monospecific flocks, subordinates fed at low rates on branches owing to frequent hostile encounters. When foraging in mixed flocks, however, subordinates foraged among leaves, and their feeding rates increased because the frequency of intraspecific interference decreased greatly. Dominants did not show any difference in feeding pattern with social situation. Thus, heterospecific flocking was more advantageous for subordinates.     

Knuckle-walking and the evolution of hominoid hands

Knuckle-walking is a pattern of digitigrade locomotion unique to African apes among Primates. Only chimpanzees and gorillas are specially adapted for supporting weight on the dorsal aspects of middle phalanges of flexed hand digits II–V. When forced to the ground, most orangutans assume one of a variety of flexed hand postures, but they cannot knuckle-walk. Some orangutans place their hands in palmigrade postures which are impossible to African apes. The knuckle-walking hands and plantigrade feet of African apes are both morphologically and adaptively distinct from those of Pongo, their nearest relative among extant apes. These features are associated with a common adaptive shift to terrestrial locomotion and support placing chimpanzees and gorillas in the same genus Pan. It is further suggested than Pan comprises the subgenera (a) Pan, including P. troglodytes and pygmy chimpanzees, and (b) Gorilla, including mountain and lowland populations of P. gorilla. African apes probably diverged from ancestral pongids that were specially adapted for distributing their weight in terminal branches of the forest canopy. Early adjustments to terrestrial locomotion may have involved fist-walking which later evolved into knuckle-walking. Orangutans continued to adapt to feeding and locomotion in the forest canopy and their hands and feet became highly specialized for four-digit prehension. Although chimpanzees retained arboreal feeding and nesting habits, they moved from tree to tree by terrestrial routes and became less restricted in habitat. While adapting to a diet of ground plants gorillas increased in size to the point that arboreal nesting is less frequent among them than among chimpanzees and orangutans. Early hominids probably diverged from pongids that had not developed prospective adaptations to knuckle-walking, and therefore did not evolve through a knuckle-walking stage. Initial adjustments to terrestrial quadrupedal locomotion and resting stance probably included palmigrade hand posturing. Their thumbs may have been already well developed as an adaptation for grasping during arboreal climbing. A combination of selection pressures for efficient terrestrial locomotor support and for object manipulation further advanced early hominid hands toward modern human configuration.     

Positional behavior of long-tailed macaques (Macaca fascicularis) in northern Sumatra

Although the majority of extant primates are described as "quadrupedal," there is little information available from natural habitats on the locomotor and postural behavior of arboreal primate quadrupeds that are not specialized for leaping. To clarify varieties of quadrupedal movement, a quantitative field study of the positional behavior of a highly arboreal cercopithecine, Macaca fascicularis, was conducted in northern Sumatra. At least 70% of locomotion in travel, foraging, and feeding was movement along continuous substrates by quadrupedalism and vertical climbing. Another 14-25% of locomotion was across substrates by pronograde clambering and vertical clambering. The highest frequency of clambering occurred in foraging for insects, and on the average smaller substrates were used in clambering than during quadrupedal movement. All postural behavior during foraging and feeding was above-substrate, largely sitting. Locomotion across substrates requires grasping branches of diverse orientations, sometimes displaced away from the animal's body. The relatively low frequency of across-substrate locomotion appears consistent with published analyses of cercopithecoid postcranial morphology, indicating specialization for stability of limb joints and use of limbs in parasagittal movements, but confirmation of this association awaits interspecific comparisons that make the distinction between along- and across-substrate forms of locomotion. It is suggested that pronograde clambering as defined in this study was likely a positional mode of considerable importance in the repertoire of Proconsul africanus and is a plausible early stage in the evolution of later hominoid morphology and locomotor behavior.     

Selection of sleeping trees in pileated gibbons (Hylobates pileatus)

Selection and use patterns of sleeping sites in nonhuman primates are suggested to have multiple functions, such as predation avoidance, but they might be further affected by range defense as well as foraging constraints or other factors. Here, we investigate sleeping tree selection by the male and female members of one group of pileated gibbons (Hylobates pileatus) at Khao Ang Rue Nai Wildlife Sanctuary, Thailand. Data were collected on 113 nights, between September 2006 and January 2009, yielding data on 201 sleeping tree choices (107 by the female and 94 by the male) and on the characteristics of 71 individual sleeping trees. Each sleeping tree and all trees ≥40 cm diameter at breast height (DBH) in the home range were assessed (height, DBH, canopy structure, liana load) and mapped using a GPS. The gibbons preferentially selected tall (mean=38.5 m), emergent trees without lianas. The majority of the sleeping trees (53.5%) were used only once and consecutive reuse was rare (9.5%). Sleeping trees were closer to the last feeding tree of the evening than to the first feeding tree in the morning, and sleeping trees were located in the overlap areas with neighbors less often than expected based on time spent in these areas. These results suggest avoidance of predators as the main factor influencing sleeping tree selection in pileated gibbons. However, other non‐mutually exclusive factors may be involved as well. Am. J. Primatol. 72:617–625, 2010. © 2010 Wiley‐Liss, Inc.     

Foraging Behavior and Coexistence of Two Sunbird Species in a Kenyan Woodland

We investigated the mechanism of coexistence of the rare Amani Sunbird (Hedydipna pallidigastra) and the widespread Collared Sunbird (H. collaris), within Brachystegia woodland in the Arabuko‐Sokoke Forest, Kenya. We compared how prey abundance and search strategies affect resource exploitation by the two species. We used foraging theory to direct our measures of feeding activities as influenced by sunbird species, tree species and foraging height. We evaluated invertebrate abundance among tree species at different heights within trees. The Collared Sunbird primarily used the understory, and the Amani Sunbird primarily used the upper‐canopy. Overall, the rate of prey attacks per flight of the Amani Sunbird was 2.8 times greater than that of the Collared Sunbird. The Amani Sunbird, however, used increased search and attack rates in the understory compared with the mid‐ and upper‐canopies, but the Collared Sunbird foraged similarly throughout all strata. We hypothesize that the increased foraging rate of the Amani in the understory reflects increased foraging costs due to interference from the Collared Sunbird in that stratum. Furthermore, the Collared Sunbird exploits rich patches by moving frequently from place to place. The Amani Sunbird forages slowly, with reduced travel rates, and with a greater number of prey captures within a patch. Arthropod density did not differ among the vegetative strata, but was higher in Brachystegia spiciformis and Hymenaea verrucosa than in six other tree species. We hypothesize that the Amani Sunbird appears dependent upon continued tall B. spiciformis trees within the canopy of the Arabuko‐Sokoke Forest.     

Coping with branch excision when measuring leaf net photosynthetic rates in a lowland tropical forest

Measuring leaf gas exchange from canopy leaves is fundamental for our understanding of photosynthesis and for a realistic representation of carbon uptake in vegetation models. Since canopy leaves are often difficult to reach, especially in tropical forests with emergent trees up to 60 m at remote places, canopy access techniques such as canopy cranes or towers have facilitated photosynthetic measurements. These structures are expensive and therefore not very common. As an alternative, branches are often cut to enable leaf gas exchange measurements. The effect of branch excision on leaf gas exchange rates should be minimized and quantified to evaluate possible bias. We compared light-saturated leaf net photosynthetic rates measured on excised and intact branches. We selected branches positioned at three canopy positions, estimated relative to the top of the canopy: upper sunlit foliage, middle canopy foliage, and lower canopy foliage. We studied the variation of the effects of branch excision and transport among branches at these different heights in the canopy. After excision and transport, light-saturated leaf net photosynthetic rates were close to zero for most leaves due to stomatal closure. However, when the branch had acclimated to its new environmental conditions—which took on average 20 min—light-saturated leaf net photosynthetic rates did not significantly differ between the excised and intact branches. We therefore conclude that branch excision does not affect the measurement of light-saturated leaf net photosynthesis, provided that the branch is recut under water and is allowed sufficient time to acclimate to its new environmental conditions.     

秦岭川金丝猴冬季和春季在自然栖息地的空间利用

2000年9月到2003年3月共计197天的时间里,我们采用目标动物取样法(Focalanimalsampling)和行为的全事件记录法(Alloccurrencesampling)对一群生活在秦岭北坡周至保护区内的秦岭金丝猴(Rhinopithecusroxellana)在自然栖息地内空间利用的进行了研究。当猴群在离开人工投食区进行自由活动时我们开始收集数据。结果表明:秦岭川金丝猴在不同年龄性别组的个体对植被的空间利用明显不同,它们花费每天活动的14%的时间在地面上活动,53%时间在树叉处活动,33%的时间在树冠中间活动。与其它年龄性别个体相比,成年雄性有27%的观察时间在地上活动,并且20%的取食时间或29%的休息时间是在地上的,明显地高于其它年龄性别组的个体。群体迁移时,成年雄性有53%的时间在地上移动,而只有13%的时间是在树冠层移动的。在通过不同树冠的时候,成年雄性经常会同时抓住两边再把身体摆过去。它们也经常下到地上迁移而回避在树间跳跃。相比之下,亚成年雌性和青少年猴更加经常地在低植被层和树冠层中找食和休息。它们明显地比成年猴更加频繁地在树冠中移动,却很少下地。它们还经常使用跳跃的方式通过树冠间的空隙。从观察到摔下树的事例分析,青少年猴从树上摔下来的风险比成年猴大。本文进而讨论了影响秦岭金丝猴空间分布和移动的因素,比如说身体的重量等.     

Quantitative and functional studies on the hands of the anthropoidea. I. The Hominoidea

The hands of the Hominoidea evidence four adaptive modes which distinguish the lesse apes (Hylobatidae), the orangutan (Pongo), the African apes (Pan), and man (Homo) from one another. The hands of the apes consist of compromises between manipulatory and locomotor functions because selection has operated for precision of grip as well as for special locomotor mechanisms. The human hand is almost totally devoted to manipulation. The hands of gibbons, orangutans and the African apes differ in many features that may be correlated with locomotion. The gibbons and siamang are specially adapted for ricochetal arm-swinging. The great apes possess morphological adaptations for arboreal foraging and climbing distinct from those of the hylobatids. In addition, the African apes have become secondarily adapted for terrestrial quadrupedal locomotion. Many features that distinguish the hands of chimpanzees and gorillas may be associated with the development of efficient knuckele-walking propulsive and support mechanisms.     

Ontogeny of corticotropin-releasing factor effects on locomotion and foraging in the Western spadefoot toad (Spea hammondii)

We investigated the effects of corticotropin-releasing factor (CRF) and corticosterone (CORT) on foraging and locomotion in Western spadefoot toad (Spea hammondii) tadpoles and juveniles to assess the behavioral functions of these hormones throughout development. We administered intracerebroventricular injections of ovine CRF or CRF receptor antagonist alphahelical CRF((9-41)) to tadpoles and juveniles, and observed behavior within 1.5 h after injection. In both premetamorphic (Gosner stage 33) and prometamorphic (Gosner stages 35-37) tadpoles, CRF injections increased locomotion and decreased foraging. Injections of alphahelical CRF((9-41)) reduced locomotion but did not affect foraging in premetamorphic tadpoles, but dramatically increased foraging in prometamorphic tadpoles compared to both placebo and uninjected controls. Similarly, alphahelical CRF((9-41)) injections stimulated food intake and prey-catching behavior in juveniles. These results suggest that in later-staged amphibians, endogenous CRF secretion modulates feeding by exerting a suppressive effect on appetite. By contrast to the inhibitory effect of CRF, 3-h exposure to CORT (500 nM added to the aquarium water) stimulated foraging in prometamorphic tadpoles. These tadpoles also exhibited a CORT-mediated increase in foraging 6 h after CRF injection, which was associated with elevated whole-body CORT content and blocked by glucocorticoid receptor (GR) antagonist (RU486) injections. Thus, exogenous CRF influences locomotion and foraging in both pre- and prometamorphic tadpoles, but endogenous CRF secretion in relatively unstressed animals does not affect foraging until prometamorphic stages. Furthermore, the opposing actions of CRF and CORT on foraging suggest that they are important regulators of energy balance and food intake in amphibians throughout development.     

Positional behavior ofCebuella pygmaea in Yasuni National Park, Ecuador

In terms of positional behavior, the small-bodied callitrichids are distinguished from other anthropoids by their ability to leap between and to cling to large vertical supports, feeding occasionally or frequently on sap and bark insects. In this paper, I studied the positional behavior of a group of pygmy marmosets in a hilly wet tropical forest in Yasuni National Park, Ecuador. During traveling, the animals used quadrupedal walk/bound and leaping mostly on small horizontal supports. During foraging, quadrupedal walk/bound and clambering dominated. The main foraging postures were stand and cantilever, occurring mainly on small horizontal lianas. During feeding, scansorial locomotion was used very frequently. Claw clinging was the dominant feeding posture. Furthermore, large vertical lianas and tree boles were the most frequent feeding supports. These observations would suggest that scansorial locomotion, vertical clinging, and vertical leaping are most likelynot part of the same form function complex. Vertical leaps appear to be associated with moving in the lower parts of the forest. On the other hand, scansorial locomotion and vertical clinging appear to be related to feeding on the sap of tree boles and large lianas in the lower parts of the forest.     

Central place foraging by beavers (Castor canadensis): a test of foraging predictions and the impact of selective feeding on the growth form of cottonwoods (Populus fremontii)

Summary Several predictions of central place foraging theory were tested. As predicted, beavers foraged more selectively at increasing distance from the central place. With increasing distance from the river's edge, beavers cut fewer branches and deleted small branches from their diet. Large branches were favored at all distances, which differs from patterns observed in previous studies of beaver foraging. This difference, however, is expected and supports Schoener's (1979) predictions which are based on differences between provisioning costs and item size.The selective harvesting of branches predicted by foraging theory affects plant growth form and may influence plant reproductive patterns. High rates of branch removal caused cottonwoods to develop a shrubby architecture. The importance of selective branch choice by beavers on patterns of cottonwood reproduction (i.e., delayed sexual maturity and induced cloning) is discussed.     

群体大小和觅食环境变化对东黑冠长臂猿日移动距离的影响

日移动距离是反映动物觅食努力的重要指标之一,相关研究有助于了解动物对生境的适应策略,对濒危物种的保护至关重要.东黑冠长臂猿(Nomascus nasutus)是一种极度濒危的树栖小型类人猿,主要生活在一夫二妻制的群体中,平均群体大小6.3只,目前对于该物种的日移动距离仍然缺乏足够的科学研究.我们以广西邦亮长臂猿国家级自...     

Reaching New Heights: The Effect of an Environmentally Enhanced Outdoor Enclosure on Gibbons in a Zoo Setting

Gibbons have adapted to live in the canopy layer of the rainforest. Gibbons in the wild predominantly spend their time high in the trees resting, traveling, and foraging for food. Comparatively, gibbons in the zoo often rest and search for their food terrestrially. The purpose of this study was to provide these arboreal smaller apes with more opportunities to utilize more vertical space. Six gibbons (4 Nomascus leucogenys and 2 Symphalangus syndactylus) were observed in 2 phases of an observational study. The 1st phase measured space utilization and behaviors of the zoo-housed gibbons in their original outdoor enclosures using instantaneous sampling. The 2nd phase measured the same space usage and behaviors after several modifications were made to the environmental structures in the same outdoor enclosures. A 2-way mixed-model analysis of variance tested the height utilization of the 6 gibbons. The gibbons chose to spend significantly more time outside and at higher heights when the new structures were added. This study shows that given the opportunity, gibbons will exhibit more species-appropriate behaviors.     

Composition of mixed‐species flocks and shifts in foraging location of flocking species on Hainan Island,China

A total of 134 bird species were recorded at Jianfengling, Hainan Island, in China from May 2000 to September 2004, of which 44 participated in one or more of 134 mixed‐species flocks. These flocks averaged 3.8 ± 0.2 species and 20.3 ± 1.2 individuals. Flocking propensity in a given species ranged from 1.5 to 100%. For flocking species, frequency of flocking and number of individuals in flocks was positively correlated with frequency and number in point counts. Among all species pairs with flocking frequency above 5%, cluster and correlation analysis indicated there were two principal groups of flocking birds – canopy species and understorey species: associations were positive within a group, but negative between groups. Canopy birds had a higher flocking propensity than understorey birds. They also made significantly less use of inner branches and trunks and greater use of middle branches, and foraged at a significantly greater height when in mixed‐species flocks than when solitary. For understorey bird species, there were no significant differences in foraging locations between solitary and mixed‐species flocks. Higher flocking frequency occurred in the wet season for canopy birds, but in the dry season for understorey birds. Overall patterns were consistent with the explanation that flocking enables an expansion of foraging niche by reducing the risk of predation.     

Distribution of the pulmonary artery and vein in the lung of the white handed gibbon

The lungs of four white handed gibbons (Hylobates agilis) were examined. The right pulmonary artery runs across the ventral side of the right upper lobe bronchiole, and then traverses the dorsal side of the right middle lobe bronchiole. Thereafter, it runs along the dorso-lateral side of the right bronchus, between the dorsal bronchiole system and the lateral bronchiole system, and gradually follows the dorsal side of the right bronchus. During its course, it gives off arterial branches which run along each bronchiole. The left pulmonary artery runs across the dorsal side of the left middle lobe bronchiole and then along the left bronchus as in the right lung. The branches of the pulmonary artery run mainly along the dorsal or lateral side of the bronchiole, while the pulmonary veins run mainly the medial side of the bronchioles or between them. However, in a few portions, the pulmonary veins run the lateral side of the bronchioles. Finally, they enter the left atrium with four large veins i.e. the common trunk of the right upper lobe vein and right middle lobe vein, right lower lobe pulmonary venous trunk, left middle lobe vein, and left lower lobe pulmonary venous trunk.     

Pollinator activity can explain variation in outcrossing rates within individual trees

Abstract We tested the hypothesis that the previously recorded higher outcrossing rates and numbers of seeds per capsule from the upper, than from the lower, branches of trees of Eucalyptus globulus (Myrtaceae) is the result of greater pollinator activity in the upper parts of the canopy. Observations of bird pollinators on 23 trees, with flowers distributed evenly between the upper and lower halves of canopies, supported this hypothesis. Birds spent significantly more time foraging, and commenced foraging significantly more often, in the upper halves than in the lower halves of canopies. Flowers in the upper halves of E. globulus canopies would therefore be expected to receive more outcross‐pollen from bird pollinators because they are usually visited more often and would probably receive a greater ratio of outcross‐ to self‐pollen. We propose that such variation in pollinator activity and outcross‐pollen deposition results in different selective pressures on the mating system and pollination syndrome in different parts of the canopy. This may result in balanced selection for these traits, contributing to the maintenance of the mixed mating and generalized pollination systems of E. globulus.     

The function of ischial callosities

Ischial callosities are generally related to the sitting positions of cercopithecoid monkeys, gibbons, and siamangs, but the selective advantage of ischial callosities to the sitting postures of these animals is uncertain. It is suggested that ischial callosities are adaptations that evolved for comfortable and stable sitting on thin branches during feeding in the peripheral branch zone. It is further suggested that prehensile tails in larger New World monkeys also developed as mechanisms for exploitation of food resources found among terminal branches. Small platyrrhine monkeys do not possess any structural adaptations to peripheral branch feeding because their body size permits them to efficiently exploit small or large branches for food. Pongids are in the process of losing their ischial callosities because their large body size precludes sitting on thin branches.     

Substrate Size and Primate Forelimb Mechanics: Implications for Understanding the Evolution of Primate Locomotion

International Journal of Primatology - Did the anatomical and locomotor specializations of primates evolve in response to requirements of locomotion and foraging on thin branches? Laboratory...     

Habitat use by yellowheads,Mohoua ochrocephala (Aves: Muscicapidae), in the Hawdon River Valley,Arthur’s Pass National Park. 2. Time budgets and foraging behaviour

Abstract

Instantaneous sampling was used to describe the ecological niche of yellowheads. Observations began during nesting in 1983 and continued until April 1984. Yellowheads spent on average 90% of their time foraging. As daylength decreased, an increasing proportion of time was spent foraging and a decreasing proportion of time was spent on social activities. When feeding nestlings, females spent significantly more time foraging than did males. Yellowheads spent 75% of their time in the upper understorey and the shaded canopy. There was no difference in the relative use of strata in the two canopy tree species, nor a sexual difference in the time spent in each strata. Yellowheads were entirely insectivorous. Prey items were recorded on 33 occasions; most were lepidopteran larvae. The most common foraging method was surface gleaning, most often on foliage and trunks. Time spent foraging on different substrates varied with tree diameter and tree species. Relative use of different foraging methods changed during the study, as did the types of substrates searched for prey and the proportion of time spent in different strata and at different heights in the forest. Presumably these changes were in response to variations in invertebrate availability.