AGE AND LENGTH AT WEANING AND DEVELOPMENT OF DIET OF PANTROPICAL SPOTTED DOLPHINS, STENELLA ATTENUATA, FROM THE EASTERN TROPICAL PACIFIC

Using stomach contents from 203 spotted dolphins ( Stenella attenuata ) killed in the yellowfin tuna fishery, we modeled the weaning process of calves. Spotted dolphins began to take solid food at approximately 6 mo of age, or 115 cm, but continued to suckle until they were nearly 2 yr old. Calves tended to feed more frequently on squid as they got older, which suggested there was a shift in diet during weaning. The average age and total body length at weaning was estimated to be 0.8 yr (approximately 9 mo) and 122 cm. The oldest suckling calf was almost 2 yr old, which suggests that some calves continued to suckle for more than a year after they could have been weaned. A better understanding of the weaning process, especially quantifying the period of time when calves are nutritionally dependent on their mothers may lead to a better evaluation of their potential vulnerability to the disturbance caused by the yellowfin tuna purse-seine fishery.     

Induced orphaning reveals post-weaning maternal care in reindeer

A common by-product of human harvesting is orphaning of calves in autumn. Despite this, there are few studies in northern and temperate ungulates evaluating the fate of orphaned calves and the potential benefits to offspring and costs to mothers of post-weaning maternal care. We manipulated orphaning and forage distribution during winter for two herds of reindeer (Rangifer tarandus): one nonfed and the other supplementally fed to increase level of interference competition. Both herds consisted of females with and without calves at heel and orphaned calves. We measured survival and somatic losses during winter and distances between mother–calves and adult females–orphans within the herds. All females survived the winter, and there was no evidence of post-weaning maternal cost in terms of female’s mass loss. The winter mortality among calves was negligible and did not differ between orphans as compared to nonorphans. However, nonorphaned calves lost less mass and stayed closer to their mothers than orphans to adult females, suggesting that increased mortality might occur in harsher winters. This tended to be more marked in the fed group where interference competition was more likely due to feed being concentrated both in space and time. Reduced mass loss in nonorphans is therefore most likely due to mothers sharing and defending feeding resources and protecting their offspring from harassment by other herd members during their first winter. We conclude that hunting practise of northern and temperate ungulates where females having calf/calves at heel are intentionally or non-intentionally harvested, may have demographic side effects at least in harsh winters.     

Foraging behavior related to habitat characteristics in the invasive wasp Vespula germanica

When foraging on carrion resources, the wasp Vespula germanica usually makes repeated visits to the feeding site until depleting the resource. In the present study we analyzed how environmental cues affect wasps' behavior when re‐locating a protein food source. We studied this behavior in two different natural habitats: closed and open habitats. As closed habitats have more references to orient wasps to the feeding site than open habitats, we hypothesized that they would return to the foraging site more frequently in closed habitats than in open ones. We tested this hypothesis by studying wasp behavior in three different natural habitat conditions: (i) closed habitats, (ii) open habitats, and (iii) open habitats artificially modified by adding five sticks with flagging. Experiments consisted of training individual wasps to feed from a certain array, and at the testing phase we removed food and displaced the array by 60 cm. Therefore, we recorded wasps’choices when returning to the training area, by counting both the wasps’first approaches and the number of visits to the original feeding site and the displaced array. Wasps' behavior while re‐locating a protein food source was different if foraging at open or closed habitats. Wasps more frequently revisited a previous feeding location when foraging in closed habitats than when foraging in open ones. Furthermore, wasps more frequently visited the displaced array than the original feeding site in all three treatments. Nevertheless, when wasps were trained in closed habitats, they returned to the original feeding site more frequently than if trained in open ones. Interestingly, when five sticks with flagging were added in open habitats, wasps responded similarly as in closed habitats without these references. The results show that foraging behavior in V. germanica seems to be different in closed and open habitats, probably associated with the existence of references that guide foragers when re‐locating undepleted resources.     

Description of the basic features of parent‐offspring stomodeal trophallaxis in the subsocial wood‐feeding cockroach Salganea esakii (Dictyoptera,Blaberidae, Panesthiinae)

In subsocial xylophagous cockroaches it is thought that parental feeding is important for the survival and growth of the altricial offspring, but the details of parental feeding in these groups are poorly known. We observed stomodeal (oral) trophallaxis between parents and the 2nd or 3rd instars of the wood‐feeding cockroach Salganea esakii Roth, and here report basic features of trophallaxis in young families. Both the female and male parents fed young nymphs with stomodeal food, and there was no difference in the frequency of the behavior between parental sexes. Up to three nymphs could be fed simultaneously during a single trophallactic event. Adults occasionally rejected contact with nymphs by blocking them with their forelegs. Nymphs utilized trophallactic food from parents more frequently than feeding independently on wood pieces or fecal pellets. Trophallaxis between sibling nymphs was never observed. These results suggest that the 2nd and 3rd instar nymphs rely on the stomodeal substances provided by their parents, and that provisioning is an essential component of subsocial behavior in biparental wood‐feeding cockroaches.     

Social Effects of Maternal Age and Experience in Bison: Pre- and Post-weaning Contact Maintenance with Daughters

Effects of maternal age and experience on long-term contact maintenance interactions with female offspring were examined in bison (Bison bison), as part of a study of factors influencing dyadic behavioural interaction. During the first five months, patterns of change in interactions varied with maternal age and parity. Young (largely primiparous) mothers and their calves steadily increased the frequency with which they maintained contact, while older mothers and their calves became increasingly independent (e.g. calves walked away from mothers more and followed them less often). Filial independence was most extreme in the (last) calves of the two oldest mothers. These age-specific patterns appeared to result largely from contrasting shifts in maternal behaviour from Month 1 to 2; differences between groups before and after this shift were opposite in direction. In the first month, older mothers maintained more frequent contact and were behaviourally more synchronized with their calves. After the first month, however, the efforts of older mothers to maintain dyadic proximity abruptly decreased, while those of young mothers and their calves gradually increased. Subsequent differences between groups were more consistent. Young mothers and their daughters maintained closer contact and continued to do so well past weaning, at least as late as the third year, when daughters reached sexual maturity. Filial behaviour played an important role in determining patterns of dyadic spatial relations; the close proximity maintained by young mothers and their offspring appeared due largely to the frequency with which these calves followed their mothers' movements. The relatively independent calves of older mothers took greater initiative in contact interactions with mothers (e.g. nosing, licking). Young mothers appeared to strengthen long-term bonds with daughters by initiating contact frequently; the closeness of post-weaning dyadic association increased with the frequency of pre-weaning maternal contact.     

Allonursing in Captive Guanacos,Lama guanicoe: Milk Theft or Misdirected Parental Care?

Females in several ungulates transfer milk to non-filial (NF) offspring, in a process known as allonursing. This behavior is less common in monotocous species, including most ungulates, and it has been associated with parasitic behavior of calves or mothers who have lost their own offspring. To examine whether the calves 'steal' milk from the females or whether females fail to discriminate their own calves in guanacos, allonursing behavior was observed. If milk theft drives allonursing, mothers should reject NF offspring, they should search for their own calves, and calves attempting to suckle from alien mothers should adopt parallel (as opposed to the anti-parallel) position during allonursing. Alternatively, if allonursing is caused by mothers unable to discriminate own offspring, mothers are not expected to reject NF offspring, and alien calves should use parallel and antiparallel position similarly when allonursing. Allonursing was investigated during the first 3 mo of lactation in two groups of captive guanacos composed of 15 and 14 mother-calf pairs, respectively. While 40% and 62.5% of mothers in groups 1 and 2 performed allonursing, high individual variation prevailed; some females exhibited this behavior infrequently (4.1% and 6.5 % in groups 1 and 2). The rejection rate to NF nursing attempts was threefold higher than the rejection rate to filial nursing attempts. The occurrence of nursing to NF was associated to a parallel posture by the calves. Our findings suggest that 'milk theft' is a more plausible hypothesis to explain allonursing in guanacos than 'misdirected parental care'.     

Mother–calf interactions and social behavior development in Commerson’s dolphins (Cephalorhynchus commersonii)

Mother–calf interactions and the behaviors of mothers during separation from their calves were examined in four Commerson’s dolphin (Cephalorhynchus commersonii) mother–calf pairs. Four infants were observed: 56.8 h over 30 days from birth to 263 days of age, 36.9 h over 20 days from birth to 149 days of age, 10.4 h over 3 days from birth to 2 days of age, and 15.0 h over 3 days from birth to 2 days of age. All four pairs shared common characteristics in the rate and frequencies of mother–calf interactions and the behaviors of mothers during the first week of life. After the first week, individual differences in changes in the frequency of each behavior were observed. The three behaviors considered representative of maternal care (parallel swimming, synchronous breathing, and body-to-body contact) were frequently performed in the first week; thereafter, the frequencies declined. Separate behaviors of mothers were infrequent during the first week and increased with an increase in infants’ age. Bumping by infants increased with time, suggesting an increase in soliciting by calves and conflict between mothers and calves. The frequency of flipper-to-body rubbing also changed but in a complex manner, probably because the calves needed to learn how to perform this behavior from their mothers and because initiator and recipient of this behavior can be changed quickly.     

Foraging Strategy within African Elephant Family Units: Why Body Size Matters

Differences in intraspecific foraging strategies have been documented between sexes of strongly dimorphic large herbivore species. Body size implications on diet quality requirements, however, can be extended to within‐species age‐specific comparisons. We investigated the hierarchical separation of foraging behavior at the scale of plant type, plant species, plant part and vertically through the canopy. For this, we studied African elephant adult females (lower quality diet required) and weaned calves (higher quality diet) within the elephant family unit, which is socially constrained to traverse the landscape together. Grass and browse were used with similar seasonal frequency. Both females and calves tracked the phenology of woody species, including these species in the diet when new growth was available. Forage utilization differed at the plant part level, with calves selecting for less fibrous and more nutritious plant parts (e.g., stripped leaves), while adult females selected branches, bark and roots with greater frequency. There was displacement of females to higher foraging levels in the canopy when these females fed <3 m away from calves. Elephant family unit foraging strategies were driven by body size, age‐specific nutritional requirements and intraspecific competition. This has broader application to other large herbivore species with great variance in intraspecific body size.     

Florida Scrub-Jays (Aphelocoma coerulescens) are Sentinels More When Well-Fed (Even with no Kin Nearby)

Sentinels occupy high, exposed positions while other group members forage nearby. If sentinel behavior involves a foraging–predation risk trade‐off, animals should be sentinels more when fed supplemental food. When individual Florida scrub‐jays (Aphelocoma coerulescens) were fed fragments of peanuts, during the following 30 min they shifted 30% of their time from foraging to sentinel behavior. In a follow‐up experiment, we fed either one or two members in each group. As before, the jays reduced their foraging and spent much more time as sentinels when given supplemental food. In each treatment, pairs were sentinels simultaneously considerably less often than expected by chance. The dramatic shift from foraging to sentinel behavior suggests that for Florida scrub‐jays sentinel behavior brings substantial benefits for no greater cost than that of lost opportunities to forage. Because the results held for simple mated pairs of scrub‐jays, we argue that kin selection and social prestige are not necessary to explain sentinel behavior.     

Determining optimum age of Holstein dairy calves when adding chopped alfalfa hay to meal starter diets based on measures of growth and performance

The present study was conducted to determine the optimum age of Holstein dairy calves for an effective inclusion of alfalfa hay (AH) in starter feed on performance, apparent digestibility and feeding behavior. A total of 40 Holstein dairy calves (20 female and 20 male) were used in a completely randomized design in which calves were randomly assigned to one of four different dietary treatments including control (CON) calves fed starter feed without any forage and three treatments consisting of the same starter feed plus 15% chopped AH fed when calves were at the 2^nd (AH2), 4^th (AH4) or 6^th (AH6) week of age. Calves were individually housed and bedded with sand that was replaced every other day. Feed and water were available ad libitum throughout the experiment. Calves were fed milk at 10% of birth BW twice daily until d 57. The study concluded when calves were 73 days old. Starter intake was recorded daily and BW was measured weekly. Data were analyzed as a complete randomized design by MIXED procedures of SAS. Results demonstrate that calves receiving AH treatments numerically consumed more starter feed (0.62 v. 0.78, 0.71 and 0.65 kg/day for CON, AH2, AH4 and AH6, respectively) and had greater average daily gain (ADG) compared with CON (0.48 v. 0.57, 0.49 and 0.49 kg/day for CON, AH2, AH4 and AH6), although the significant difference was observed only between AH2 and CON. Among AH treatments, calves in AH2 had better performance than AH6 in several cases including starter intake, ADG. No detectable differences were observed, however, in apparent dry matter, organic matter or CP digestibility among treatments. Ruminal pH and NH₃ concentrations, measured on weeks 4, 6, 8 and 10, were lower for calves fed CON compared with other treatments, with ammonia concentrations decreasing over time. Calves in the AH treatments spent more time eating and ruminating compared with CON. Calves fed CON, however, spent more time on laying down compared with other treatments. Overall, results from the present study illustrated that inclusion of alfalfa in starter feed for calves at 2 weeks of age may improve feed intake, ADG and stimulate rumination in young Holstein dairy calves. Results, however, should be viewed with caution as the number of calves per treatment was small and large calf-to-calf variation may have affected the results reported.     

Behavioral processes and costs of co-existence in female spotted hyenas: a life history perspective

We assessed the importance of three behavioral processes on the fitness of individual females as mediated via maternal care in matrilineally organized social groups of spotted hyenas Crocuta crocuta. These were maternal choice of foraging tactic, the maintenance of individual dominance rank (social status) within the adult female hierarchy, and the behavioral support provided by mothers to their daughters when daughters acquired their position in the adult female hierarchy. The effects of all behavioral processes were closely linked. Maternal care was dependent on maternal social status because high ranking females had priority of access to food, and individual maternal choice of foraging tactic was frequency – and social status-dependent when medium prey abundance provided an opportunity for such a choice. At medium prey abundance, low ranking females went on costly long distance commuting trips to forage on migratory herds outside the group territory, whereas high ranking females fed on kills within the group territory. As a consequence, offspring of high ranking females grew faster, had a higher chance of survival to adulthood, and thus high ranking females had a higher lifetime reproductive success. Daughters of high ranking females usually acquired a social status immediately below that of their mother provided they enjoyed the effective support from their mothers as coalition partners, and they gave birth to their first litter at an earlier age than daughters of low ranking mothers. Spotted hyenas are therefore an example of the silver-spoon effect. This study shows that the frequency-dependent outcome of behavioral processes can be a key determinant of maternal reproductive success in social carnivores and have a profound influence on the reproductive career prospects of offspring.     

Food allocation in crimson rosella broods: parents differ in their responses to chick hunger

Food allocation in many asynchronously hatching bird species favours large, competitively superior chicks. In contrast, food is usually distributed equally within broods of crimson rosellas, Platycercus elegans, implying that parents do not simply feed the most competitive chick. We used two temporary removal experiments to manipulate hunger of: (1) individual first- or last-hatched chicks, or (2) the whole brood. When only a single chick was hungry, parents compensated fully and chicks gained the same mass over the day as during controls. Mothers and fathers, however, responded in different ways to chick hunger. Mothers did not strongly alter their food allocation when a single chick was hungry, and controlled the distribution of food by refusing to feed first-hatched chicks when they were hungry and by moving more during feeds. In contrast, fathers allocated more food to hungry last-hatched chicks. When the whole brood was hungry, parents were unable to compensate chicks and all chicks lost mass over the day. In these conditions, mothers preferentially fed first-hatched chicks, while fathers fed all chicks equally. Our results show that both mothers and fathers were able to discriminate and selectively feed chicks, but that parents responded differently to changes in chick hunger within the brood. Fathers responded more strongly to variation in chick hunger within the brood, suggesting they reallocate food based on short-term changes in hunger. Mothers distributed food preferentially to last-hatched chicks except when the whole brood was hungry, when they switched to favouring first-hatched chicks. This pattern is consistent with a strategy of adaptive brood reduction when food is scarce. Copyright 2000 The Association for the Study of Animal Behaviour.     

The importance of honeydew as food for larvae of Chrysoperla carnea in the presence of aphids

Larvae of the common green lacewing Chrysoperla carnea are predacious and feed on a wide range of small, soft‐bodied arthropods. In addition to their feeding on prey arthropods to cover their nutritional requirements for growth and development, the consumption of non‐prey foods such as honeydew has been reported. It is commonly believed that these food supplements are primarily exploited by the larvae when prey is scarce or of low nutritional quality. Here, we assess whether C. carnea larvae also use honeydew when high‐quality aphid prey are readily available. In a choice experiment, the feeding behaviour of C. carnea larvae was observed in the presence of both aphids and honeydew. The larvae were starved, aphid‐fed, or honeydew‐fed prior to the experiment. The time spent feeding on honeydew compared with feeding on aphids was highest for starved larvae and lowest for honeydew‐fed larvae. Among the three treatments, the aphid‐fed larvae spent the most time resting and the least time searching. In an additional experiment food intake was assessed in terms of weight change when larvae were provided with an ad libitum supply of either aphids or honeydew. Larvae yielded a significant lower relative weight increase on honeydew compared with aphids. The reduced weight increase on honeydew was compensated when larvae were subsequently provided with aphids, but not when honeydew was provided again. This study showed that (i) prior honeydew feeding reduces overall aphid consumption, and (ii) larvae do consume honeydew even after they have been given ad libitum access to aphids. The fact that larvae of C. carnea still use honeydew as a food source in the presence of suitable prey underlines the importance of carbohydrates as foods.     

Quantitative observations on feeding behavior inSaguinus geoffroyi (callithricidae,primates)

Feeding behavior of a six-animal group of marmosets,Saguinus geoffroyi, was observed under field conditions in the Panama Canal Zone. The order of feeding was recorded as the marked animals fed from a limited access food source. A combined distribution of observed visitations to the food source was shown to be significantly non-random (p<.005). The juveniles of the group were seen to feed at the source before adults on the average.     

Host plant choice in the comma butterfly-larval choosiness may ameliorate effects of indiscriminate oviposition

In most phytophagous insects, the larval diet strongly affects future fitness and in species that do not feed on plant parts as adults, larval diet is the main source of nitrogen. In many of these insect-host plant systems, the immature larvae are considered to be fully dependent on the choice of the mothers, who, in turn, possess a highly developed host recognition system. This circumstance allows for a potential mother-offspring conflict, resulting in the female maximizing her fecundity at the expense of larval performance on suboptimal hosts. In two experiments, we aimed to investigate this relationship in the polyphagous comma butterfly, Polygonia c-album, by comparing the relative acceptance of low- and medium-ranked hosts between females and neonate larvae both within individuals between life stages, and between mothers and their offspring. The study shows a variation between females in oviposition acceptance of low-ranked hosts, and that the degree of acceptance in the mothers correlates with the probability of acceptance of the same host in the larvae. We also found a negative relationship between stages within individuals as there was a higher acceptance of lower ranked hosts in females who had abandoned said host as a larva. Notably, however, neonate larvae of the comma butterfly did not unconditionally accept to feed from the least favorable host species even when it was the only food source. Our results suggest the possibility that the disadvantages associated with a generalist oviposition strategy can be decreased by larval participation in host plant choice.     

Food sharing in lion tamarins: Tests of three hypotheses

Infant marmosets and tamarins (Callitrichidae) frequently receive food from older group members. Three possible functions of food sharing in lion tamarins were examined experimentally. The first hypothesis, that food sharing ensures that infants receive sufficient food even if it is difficult for them to acquire it themselves, was tested by varying the ease with which infants could reach a food source. When access to food was restricted, infants fed themselves less, received more food from others, and had a higher success rate in begging attempts. The second hypothesis, that food sharing helps teach infants an appropriate diet, was tested by presenting fruits that were novel to infants. Although infants fed themselves less under these conditions, adults were less likely to share novel foods than familiar foods. The final experiment compared food sharing when food was abundant with behavior when food items were presented singly. Infants fed themselves less and received more food from others when food items were rare. These results suggest that food sharing in lion tamarins helps to ensure that infants receive adequate amounts of food which is difficult to locate or acquire, but that it is not involved in teaching infants which foods they should eat. © 1993 Wiley-Liss, Inc.     

The effects of twinning and maternal experience on maternal-filial social relationships in confined beef cattle

The objective of this investigation was to assess the maternal-filial social relationships of Hereford beef cattle as influenced by maternal experience of the dam (primiparous vs. multiparous) and number of offspring (one vs. two calves). Calves were temporarily separated from their dams during the first week after parturition, and the behavioral responses of mother and young were noted during and following separation.Contact and contact-seeking behaviors between twins and their mothers began to decline by the 5th or 6th day post-partum. Over the same period, contact behaviors exhibited by single calves and their dams remained stable or increased in frequency. Mothers of twins were less responsive to their calves than mothers of singles both during and following separation, and twins interacted with alien females more frequently than single-born young. It is proposed that insufficient milk production by Hereford dams bearing two calves provides an incentive for twins to parasitize the milk supply of alien mothers and, thus, become less dependent on their natural mothers. Social feedback between mother and twins may be further reduced by dams dividing their maternal attentiveness between two offspring.In general, experienced cows were more responsive to separation from their offspring than inexperienced heifers. Cows and their calves exhibited more frequent contact and contact-seeking behavior than heifers and their young.     

The effects of twinning on mother—Offspring behavior in range beef cattle

Methods to increase the productivity of beef cattle include induced twinning and multiple fostering of calves on nurse cows, but little is known about the capacity of cows to rear more than one calf in a rangeland environment.Eight single and 14 twin calves and their mothers were studied in a 30.4-ha enclosure in a California rangeland environment from 2 to 20 weeks following parturition. Data were obtained on ingestive, grooming, agonistic, play and sexual behaviors, as well as spatial proximity of calves to mothers and peers.Initially, twins spent more time suckling their mothers than did single calves (presumably due to insufficient milk intake), but later adapted by utilizing natural forage and obtaining milk from alien cows. By 15–20 weeks of age, twins were suckling their dams for less than one-quarter of the time spent at 3–6 weeks, whereas the suckling time of single calves did not decline. Thus, twins may experience a natural early weaning from mother's milk.The hypothesis that mother—Offspring bonds are weaker with twins than with singles was supported by the fact that mothers bearing twins groomed their offspring less than mothers with singles, and twins were normally found at greater distances from their mothers than singles.Most long-distance cow—Calf separations resulted from the cow moving to feed or to obtain water. Reunion of mother and young depended on auditory communication; the calf normally traversed most of the intervening distance.     

Florida Scrub-Jays Compensate for the Sentinel Behavior of Flockmates

Sentinel coordination requires that individuals react to the sentinel behavior of others. Previous work showed that Florida scrub‐jays are sentinels more often when given supplemental food. Here we measured how birds in pairs reacted when their mates were fed. Scrub‐jays were sentinels less when their mates were fed, demonstrating compensation. Indirect evidence suggests that this compensatory decrease in sentinel behavior was smaller than the increase in sentinel behavior by their mates. In addition, males in newly established groups were sentinels less often.