Progressive parenting behavior in wild golden lion tamarins

Young primates in the family Callitrichidae (the marmosets and tamarins) receive extensive and relatively prolonged care from adults. Of particular note, callitrichid young are routinely provisioned until well after weaning by parents and helpers, which is in stark contrast to typical juvenile primates, who must acquire most of their food independently once they are weaned. Adults of some callitrichid species produce a specialized vocalization that encourages immature group members to take proffered food from the caller. Here, I report that wild adult golden lion tamarins (Leontopithecus rosalia) not only used this food-offering call to encourage young, mobile offspring to approach and take captured prey from them, but as the young began to spend significant time foraging for themselves and to acquire prey by independent means, the frequency of these vocalizations in the context of food transfer declined. Adults then began to use food-offering calls in a novel context: to direct juveniles to foraging sites that contained hidden prey that the adults had found but not captured. During the period of these most frequent adult-directed prey captures, the independent prey-capture success rates of juveniles improved. Thus, adults modified their provisioning behavior in a progressive developmentally sensitive manner that may have facilitated learning how to find food. I hypothesize that as a result of these demonstrations by adults, juveniles either may be encouraged to continue foraging despite low return rates or to learn the properties of productive prey-foraging substrates in a complex environment.     

Begging for information: mother-offspring food sharing among wild Bornean orangutans

Transfer of solid food from mothers or other adults to dependent offspring is commonly observed in various primate species and both nutritional and informational benefits have been proposed to explain the function of such food sharing. Predictions from these hypotheses are tested using observational data on wild orangutans (Pongo pygmaeus wurmbii) at Tuanan, Central Borneo, Indonesia. In 1,145 hr of focal observation and 458 recorded food interactions between four pairs of females with offspring it was found that virtually all transfers were initiated by the offspring and that younger infants solicited food more often and did so for a greater variety of items than older offspring. All offspring primarily solicited food that was difficult to process, i.e., inaccessible to them. Furthermore, the amount of food solicitation was negatively correlated with ecological competence. Hence food sharing seemed to be related to an offspring's skill level, as suggested by the informational hypothesis. In contrast, offspring did not solicit high-quality items more than low-quality items and food sharing did not peak around the age of weaning, as predicted by the nutritional hypothesis. Mothers were usually passively tolerant, allowing offspring to take food but hardly ever provisioned. Parent-offspring conflict concerning food sharing was only observed well after weaning. Thus, by taking food directly from the mother, young orangutans were able to obtain information about the affordances and nutritional value of food items that were otherwise out of their reach and could familiarize themselves with the mother's diet. In species such as orangutans or other apes, characterized by a broad diet that requires extractive foraging, informational food transfer may be vital for an immature to acquire complex feeding skills and adult diet.     

Determinants of dietary specialization: a comparison of two sympatric species of sea snakes

Why do some predator species specialize on only a single type of prey whereas others take a broad range? One critical determinant may be the ontogenetic range of body sizes of the predator compared to that of its prey. If any single prey taxon spans only part of the range of prey sizes ingestible by the predator, then the predator will be more likely to take multiple prey taxa. We exploit a model system that provides a robust opportunity to test this hypothesis. We studied two sympatric species of predatory sea snakes, similar in size and general ecology that feed on anguilliform fishes from different habitats in the Great Lagoon of New Caledonia. Eel species from soft‐bottom habitats must construct their own burrows, and thus tend to be more slender‐bodied and less variable in body size than eel species that inhabit variable‐sized crevices among hard coral. As a result, a laticaudine sea snake species (Laticauda saintgironsi) that feeds on hard‐coral‐dwelling eels relies primarily on a single prey species: juveniles take young eels whereas adults consume adult eels of the same species. In contrast, a laticaudine species (L. laticaudata) that forages on soft‐bottom eels switches its prey ontogenetically: juveniles take small eel species whereas adults consume large eel species. Thus, habitat‐imposed constraints on the range of body sizes within each prey taxon generate a striking difference in the degree of dietary specialization of two closely related, sympatric predator species.     

Life cycle period and activity of prey influence their susceptibility to predators

In a multi‐prey system, predators kill different kinds of prey according to their availability, where “availability” is a function of prey abundance and vulnerability (e.g. anti‐predator behavior). We hypothesized that prey availability changes seasonally, for instance because reproduction leads to a higher abundance of young in spring and summer or because changes in behavior such as during the mating season makes the prey periodically more vulnerable. We tested this hypothesis in a simple predator‐prey system in the Jura Mountains of Switzerland and France, where a single large mammalian predator, the Eurasian lynx, preys upon two ungulate species, the roe deer and the chamois. In 1996 and 1997 we were able to assign a total of 190 roe deer and 54 chamois killed by lynx to a specific age and sex class (males, females or juveniles). As expected, the proportion of juveniles killed varied considerably among periods, being at the highest from 1st of June to 15th of August. No significant seasonal differences were detected regarding the frequency of predation on males versus females. In particular, the interaction between species and period, expected because of different timing of the rutting period between roe deer and chamois, was not significant. Females were killed only slightly more often during gestation. The relationship between prey abundance and vulnerability is highly complex, as the lynx’ prey selection needs to be analyzed not only horizontally (changes of a specific prey category with season) but also vertically (an increase in the vulnerability of one category releases predation pressure on others). Second, we predicted that certain activities, such as feeding, expose prey to predation more than others. We found more chamois predated when feeding, whereas roe deer were predated mainly when ruminating. This interspecific discrepancy reflects differences either in the anti‐predator behavior of roe deer and chamois or in the relative time allocation to feeding and ruminating between the two species.     

Foraging for animal prey by outdoor groups of Geoffroy’s marmosets (Callithrix geoffroyi)

I studied animal prey foraging by three outdoor groups of Geoffroy’s marmosets, Callithrix geoffroyi, over the course of two summers (June–August 1994; August–September, 1995. Marmosets are highly motivated to forage for animal prey, as demonstrated by the amount of time spent foraging for insects and small vertebrates even in the presence of provisioned, high-quality food. Like their wild congeners, the marmosets engaged in prolonged visual searches of selected areas while slowly locomoting. They seldom used their hands to manipulate substrates. The marmosets were startled proportionately more often while foraging for animal prey than would be predicted by their overall time budgets, and they regularly, if briefly, interrupted their search/locomote pattern with sweeping scans of the surroundings that may contribute to a vigilance function. While carrying infants, they almost never foraged. These results are consistent with the notion that marmosets may be particularly vulnerable to predation while searching for animal prey. Most of the data on marmoset and tamarin feeding ecology have focused on fruits and gums. My data underscore the need to understand better the role of animal prey in the behavioral ecology of callitrichids.     

Patterns of nest provisioning and parental investment in the solitary digger wasp Ammophila sabulosa

Abstract.

• 1 In nest-building wasps there is a continuum from species that provision each offspring cell with one large prey item (single provisioning) to species that provision each cell with many small items (multiple provisioning). The significance of number of prey per cell was examined during two seasons in Ammophila sabulosa (L.), a species that provisions between one and five caterpillars per cell.
• 2 There was no difference between the total weight of prey in singly-provisioned and multiply-provisioned cells: individual caterpillars placed in multiply-provisioned cells were smaller.
• 3 Small caterpillars were captured and transported to the nest faster than large ones.
• 4 If the first prey provisioned was large, the cell was usually then permanently closed. If the first prey was small, additional prey were captured, and females appeared to become more selective: additional prey were rarely large.
• 5 It is suggested that the flexible provisioning strategy used by A.sabulosa allows a wide range of prey sizes to be utilized without affecting maternal control of offspring size and sex. This could be important when available prey sizes vary temporally and spatially.
• 6 There was a male-biased first generation investment ratio. Female-producing cells were provisioned with a higher total prey weight than male-producing cells, and conversion of prey weight to adult weight was more efficient for females.
• 7 Total prey weight provisioned is probably a good indirect measure of parental time investment in A.sabulosa. Other measures, particularly number of prey provisioned, will be less accurate.

     

Disparity between Adult and Juvenile American Robins Turdus migratorius Foraging for Ground Invertebrates and Cherry Fruits

Although it has long been known that juveniles often have foraging skills inferior to those of adults, it has generally been assumed that animal prey are more difficult to capture than fruit, and thus that juveniles foraging on fruit should be similar to adults in their efficiency. To examine these ideas, we investigated the abilities of juvenile and adult American robins Turdus migratorius to forage for ground invertebrates and fruits of the black cherry tree Prunus serotina. We hypothesized that juveniles, lacking the experience of adults, would not have the skills of adults and therefore would be less proficient invertebrate and fruit foragers. Juveniles captured 69% of invertebrates at which they struck compared with 80% of adults’ strikes that ended in capture. However, juveniles made more strikes than adults, so mean prey capture per minute was the same. Juveniles were also less skilled fruit foragers. Juveniles were twice as likely as adults to fail to pick a cherry (55% of adults’ vs. 28% of juveniles’ attempts ended in success). However, there was no significant difference in the proportion of juveniles and adults that dropped a cherry once it was picked. As a result of their low levels of success, juveniles consumed about half the number of cherries per minute as did adults. Contrary to prior assumptions, skills involved in fruit foraging may not be so easily acquired and many omnivorous species, like the American robin, must learn both invertebrate and fruit foraging skills.     

Foraging ecology of the California gnatcatcher deduced from fecal samples

The California gnatcatcher is a threatened species essentially restricted to coastal sage scrub habitat in southern California. Its distribution and population dynamics have been studied intensely, but little is known about its diet. We identified arthropod fragments in 33 fecal samples of the California gnatcatcher to gain insight into its foraging ecology and diet. Fecal samples were collected from adult males, adult females, fledglings, and nestlings. Leaf- and planthoppers (Homoptera) and spiders (Araneae) predominated numerically in samples. Spider prey was most diverse, with eight families represented. True bugs (Hemiptera) and wasps, bees, and ants (Hymenoptera) were only minor components of the gnatcatcher diet. Gnatcatcher adults selected prey to feed their young that was larger than expected given the distribution of arthropod size available in their environment, and chicks were provisioned with larger prey items and significantly more grasshoppers and crickets (Orthoptera) and spiders than adults consumed themselves. Both adults and young consumed more sessile than active prey. Further studies are needed to determine whether arthropods sampled in coastal sage scrub that are common in fecal samples are good indicators of California gnatcatcher habitat. Received: 30 December 1998 / Accepted: 28 April 1999     

Sex differences in responsiveness to begging in a cooperative mammal

In species where young are provisioned by both parents, males commonly contribute less to parental care than females, and are less responsive to variation in begging rates. Similar differences in the care of young occur among adults in cooperative breeders, but fewer studies have investigated whether these are associated with differences in responsiveness. Here, we present results from a playback experiment investigating responsiveness to begging in the meerkat (Suricata suricatta), a cooperatively breeding mammal. Although increased begging rate raised the feeding rate of adults of both sexes, there was no consistent tendency for females to be more responsive than males. However, when we examined changes in the proportion of food items found that were fed to pups (generosity), we found that females were more responsive than males to increased begging rate. These results can be explained in terms of sex differences in dispersal: in meerkats, females are philopatric and receive considerable benefits from investing in young, both directly, by increasing group size, and indirectly, by recruiting helpers if they inherit the breeding position. In addition, they emphasize that generosity provides a more sensitive measure of responsiveness to begging than feeding rate, as it accounts for variation in foraging success.     

Foraging Ontogeny is not Linked to Delayed Maturation in Squirrel Monkeys (Saimiri sciureus)

The acquisition of complex foraging behaviors by young is a proposed cause of a prolonged juvenile phase in many vertebrates, including primates. I compared the foraging behaviors of infant, juvenile and adult squirrel monkeys to determine if significant age‐related differences in foraging behavior and efficiency were present. Infants and juveniles differed from each other in patterns of prey and fruit foraging, but few differences existed between juveniles and adults. Despite differing in the use of foraging substrates, young juveniles (8–12 mo) were as efficient as older juveniles (1–4 yr) and adults at capturing and processing large prey. Young juveniles (<1 yr) were limited in their ability to consume husked palm fruits due to an inability to peel them to obtain pulp. By 1 yr of age, however, foraging behaviors of adults and juveniles were nearly indistinguishable. The absence of meaningful differences between adults and juvenile foraging is not consistent with the hypothesis that the need to develop foraging skills accounts for the pattern of extended juvenility in squirrel monkeys.     

Age-Related Changes in Nestling Diet of the Cooperatively Breeding Green Woodhoopoe

In many socially monogamous bird species, parents of altricial young respond to the increasing demands of growing nestlings by increasing their feeding rate and the size of prey items delivered and by altering the types of prey provided. In some cooperatively breeding species, similar changes in feeding rate and prey size have been documented. However, potential changes in the types of prey delivered, both as nestlings age and by different group members, remain largely unexplored. Moreover, studies rarely compare the diet fed to nestlings with that eaten by the provisioning adults themselves. Here, I show that green woodhoopoe ( Phoeniculus purpureus ) nestlings receive a smaller proportion of spiders and larger proportions of caterpillars and centipedes as they grow older. Both male and female adults delivered a higher proportion of spiders to young nestlings than they ate while self-feeding, probably in response to particular nutritional requirements of the chicks. However, only males altered the proportions of caterpillars and centipedes delivered, providing smaller proportions to young nestlings than eaten themselves. These prey items may be too large for young nestlings to handle, and males may make a greater adjustment in provisioning diet than females because they collect more caterpillars and centipedes than do females. Although there were sex differences in provisioning diet, there were no differences between same-sex breeders and helpers in terms of the overall proportions of prey delivered or the changes with nestling age. Hence, individuals of different reproductive status may be following the same provisioning rules, at least in terms of prey type.     

Assured fitness returns in a social wasp with no worker caste

The theory of assured fitness returns proposes that individuals nesting in groups gain fitness benefits from effort expended in brood-rearing, even if they die before the young that they have raised reach independence. These benefits, however, require that surviving nest-mates take up the task of rearing these young. It has been suggested that assured fitness returns could have favoured group nesting even at the origin of sociality (that is, in species without a dedicated worker caste). We show that experimentally orphaned brood of the apoid wasp Microstigmus nigrophthalmus continue to be provisioned by surviving adults for at least two weeks after the orphaning. This was the case for brood of both sexes. There was no evidence that naturally orphaned offspring received less food than those that still had mothers in the nest. Assured fitness returns can therefore represent a real benefit to nesting in groups, even in species without a dedicated worker caste.     

Sibling competition in a brood-tending leech

Conflict among siblings over parental investment, particularly over parental feeding, is a feature of family life in many kinds of animals. In some bird species, the size of prey items provided to juveniles has been implicated as a cause of aggressive competition among sibling chicks, because prey size determines whether dominance allows monopolization of parental offerings. Our experiment was meant to test the generality of this factor in creating intrafamilial conflict. We investigated sibling competition in relation to prey size using the carnivorous, brood-tending leech Helobdella papillornata. We equalized the total amount of food available to H. papillornata broods, but varied the size of individual prey items. Competition, measured by disparity in body size at independence, was more intense in broods provisioned with small items than in broods receiving large items, but similar between broods receiving large items and broods fed ad libitum. These patterns suggest that the intensity of conflict did not depend only on the total food amount, but was enhanced by small prey size. Our results indicate that conflict over the provision of parental resources to offspring can have a similar basis across very dissimilar organisms.     

Does exogenic food benefit both partners in an ant-plant mutualism? The case of Cecropia obtusa and its guest Azteca plant-ants

In the mutualisms involving the myrmecophyte Cecropia obtusa and Azteca ovaticeps or A. alfari, both predatory, the ants defend their host trees from enemies and provide them with nutrients (myrmecotrophy). A. ovaticeps provisioned with prey and then ¹⁵N-enriched food produced more individuals than did control colonies (not artificially provisioned). This was not true for A. alfari colonies, possibly due to differences in the degree of maturity of the colonies for the chosen range of host tree sizes (less than 3 m in height). Myrmecotrophy was demonstrated for both Azteca species as provisioning the ants with ¹⁵N-enriched food translated into higher δ¹⁵N values in host plant tissues, indicating that nitrogen passed from the food to the plant. Thus, the predatory activity of their guest ants benefits the Cecropia trees not only because the ants protect them from defoliators since most prey are phytophagous insects but also because the plant absorbs nutrients.     

Activity and ranging patterns of Colombian woolly monkeys in north-western Amazonia

In this study, I revise three aspects of the socioecology of woolly monkeys (genus Lagothrix) that might give us a better understanding of the patterns found in this species: (1) the association between temporal variation in fruit abundance and diet, activity, and ranging patterns; (2) the individual trade-offs associated with living in small or large groups, and (3) the relationship between social dominance and foraging success. Using behavioral and ecological data collected during 3 years in Tinigua Park, Colombia, I found that woolly monkeys tend to avoid open-degraded forests, where fruit production is generally lower than it is in mature forests. Diet and activity budgets were highly associated with temporal patterns of fruit production. Daily path length was positively correlated with group size and monthly fruit abundance, and negatively correlated with habitat quality. I found differences in activity budgets and the diet preferences of different age/sex classes. For example, adult males rest more and juveniles play more than other classes. Juveniles and adult females without infants look for arthropods more often than adult males and females with young infants, who showed the highest frequencies of fruit feeding. Dominant adult males were not consistently the most efficient foragers on fruits according to two different indexes. Most of these results are consistent with the expectations from strong intra-group competition for resources. However, females with infants received benefits during feeding similar to those of dominant adult males, which may be mediated by differential aggression from males to other group members (juveniles and females without infants).     

Nesting biology of the potter wasp Rhynchium brunneum brunneum (Fabricius, 1793) (Hymenoptera: Vespidae: Eumeninae) in North Vietnam

Rhynchium brunneum brunneum (Fabricius, 1793) is a common species using trap nests in North Vietnam. The females chose the nest traps with diameters ranging from 5.5 to 17 mm. Nests consisted of a linear series of one to eleven brood cells separated by mud partitions. Brood cells were provisioned with caterpillars, and eggs were attached to the ceiling of the cells by a thin filament. The life history and sex ratio data of this species were recorded from April to early November. Its sex ratio is strongly male-biased, being multivoltine, likely with four generations per year, the last one overwintering in the prepupal stage. Nesting activity of the species was described with major activities such as nesting site selection, oviposition, prey collecting, and applying cell material. Only 53.3% of the provisioned cells were successful; the others were damaged by six parasitoid species or died during development for unknown reasons.     

The food and feeding relationships of larval and 0+ year juvenile fishes in lowland rivers and connected waterbodies. II. Prey selection and the influence of gape

The relative importance of taxa- and size-specific prey selection, and the influence of gape on the prey consumed by the larvae and 0+ year juveniles of four fish species were investigated in 'main river', 'marina' and 'pond' macrohabitats in the lower River Trent, England. A general sequence of ontogenetic shifts in food consumption was reflected in the electivity indices of particular prey taxa, partly due to the restrictions imposed by the gape of 0+ year fishes. Certain taxa, however, were consistently selected over others, irrespective of size, suggesting that taxa-specific, as well as size-specific, prey characteristics may be important in the selection process. There were significant, positive relationships between maximum prey (zooplankton) length and maximum gape height for larvae, but not for 0+ year juveniles. The majority of fishes, however, consumed prey substantially smaller than the maximum theoretically possible inferred from their gape. The greater size ranges of zooplankton in connected waterbodies compared with main river channels provide suitable prey for a range of developmental steps and fish species, and may, thus, enhance recruitment success.     

Sibling cannibalism in dorada under experimental conditions.

Cannibalism among embryos and larvae of Brycon moorei (Characidae) occurs during daytime and night-time, and persists under permanent darkness. Embryos and larvae of dorada provisioned with formulated feed over the first week of exogenous feeding did not survive, except for those exerting cannibalism. When oered alternative fish prey [embryos of Prochilodus magdalenae (0·5–0·8 mg) and Oreochromis niloticus (9·10 mg)], 1-day-old embryos of dorada preferred preying on these, thereby reducing early cannibalism. However, this promoted depensatory growth and more intense cannibalism later in the larval stage. Dorada provisioned with Artemia nauplii in excess showed more homogeneous growth and higher survival, most cannibalistic acts being restricted to the first 24 h of exogenous feeding, just after oral teeth were fully developed (21 h after hatching). Provisioning dorada with Artemia nauplii a few hours before their oral teeth were fully developed reduced early cannibalism from 41 to 15%. High proportions of deformed fish caused higher mortality, both directly and indirectly, as they promoted early cannibalism, depensatory growth and more intense cannibalism among larvae. The initial sorting of embryos, based on their occupation of the water column improved survival significantly during the first week of exogenous feeding, up to 52% in progenies containing <10% of deformed fish. Size-grading of larvae and young juveniles over the next 2 weeks reduced cannibalism to 2·6 and 1·9% day ⁻¹, in the first and second weeks, respectively. These results indicate that cannibalism in dorada can be mitigated eciently through appropriate rearing procedures, and open promising perspectives for the intensive culture of this fast-growing tropical species.     

Effect of Predator-Prey Phylogenetic Similarity on the Fitness Consequences of Predation: A Trade-off between Nutrition and Disease?

A largely neglected aspect of foraging behavior is whether the costs and benefits of predation vary as a function of phylogenetic (i.e., genetic) similarity between predator and prey. Prey of varying phylogenetic similarities to predators might differ in value because both the risk of pathogen transmission and the nutritional quality of prey typically decline with decreasing phylogenetic similarity between predator and prey. I experimentally evaluated this hypothesis by feeding omnivorous spadefoot toad tadpoles (Spea bombifrons, Spea multiplicata, and Scaphiopus couchii) either conspecific tadpoles or an equal mass of three different species of heterospecific prey, all of which contained naturally occurring bacteria. I also examined which prey species Spea tadpoles preferred. I found that all three species of tadpoles performed best on, and preferred to eat, prey that were of intermediate phylogenetic similarity to the predators. Prey of intermediate phylogenetic similarity may provide the greatest fitness benefits to predators because such prey balance the nutritional benefits of closely related prey with the cost of parasite transmission between closely related individuals.     

Nutritional benefits of intraguild predation and cannibalism among generalist and specialist phytoseiid mites

1. Intraguild predation and cannibalism are common among predaceous phytoseiid mites (Acari, Phytoseiidae) but the nutritional benefits gained by these processes are poorly understood. 2. The study reported here addressed the questions of whether cannibalism and intraguild predation provide different nutritional benefits and whether the ability to utilise cannibalism and intraguild predation is linked to the diet specialisation of phytoseiid mites. Specialists tested were Phytoseiulus macropilis, Galendromus occidentalis, and Neoseiulus longispinosus; generalists tested were Amblyseius andersoni, Neoseiulus cucumeris, and Neoseiulus fallacis. 3. All generalists and the specialist P. macropilis were able to complete juvenile development with both con‐ and hetero‐specific prey. Juvenile development of generalists was shorter with heterospecific prey than with conspecific prey, whereas development of the specialist P. macropilis did not differ between prey types. Only a few N. longispinosus and G. occidentalis, both specialists, reached adulthood by cannibalism but none reached adulthood by intraguild predation. 4. All generalists were able to sustain oviposition by intraguild predation. Neoseiulus cucumeris and A. andersoni laid more eggs with heterospecific prey than with conspecific prey, whereas N. fallacis had similar oviposition rates with both prey types. No specialist sustained oviposition by intraguild predation or cannibalism. 5. Overall, generalists gained equal or more nutritional benefits by intraguild predation than by cannibalism and were able to utilise phytoseiid intraguild prey as an alternative food source. Specialists gained equal or more nutritional benefits from cannibalism than from intraguild predation. For specialists, con‐ and hetero‐specific phytoseiids may be considered only a supplemental food.