Reproductive suppression and inbreeding avoidance in wild populations of co-operatively breeding meerkats (Suricata suricatta)

Meerkats live in co-operatively breeding familial groups in which reproduction is monopolised by a dominant pair of breeders. Offspring of the breeders are behaviourally subordinate, and typically remain in their natal group as sexually mature, non-breeding helpers. In this study, we investigated the proximate factors limiting subordinate reproduction. Evidence for reproductive suppression by dominants was investigated by comparing life history, behaviour and hormonal profiles of dominants and subordinates. Baseline levels of plasma luteinising hormone (LH) were significantly higher in dominant than in subordinate females. However, following an exogenous injection of gonadotrophin-releasing hormone (GnRH), both categories had comparable concentrations of circulating LH. There were no significant differences in pre- or post-GnRH challenge LH levels in dominant or subordinate males. Reproduction in both dominant and subordinate females rarely occurred in the absence of unrelated males. Given that groups typically comprise parents and offspring, lack of suitable mates emerged as the primary constraint on subordinate reproduction. When this constraint was removed, subordinates typically bred but at a lower rate than dominants. This difference in reproduction may be attributed to intrasexual competition manifested through direct interference by dominant females through subordinate evictions, infanticide and the abandoning of subordinate litters. We argue that differences in reproductive regulation within mammalian co-operative breeding systems may be explained by differences in the mating strategy (inbreeding versus outbreeding) and the probability that subordinates in obligate outbreeding species will encounter unrelated opposite-sex partners. Received: 19 April 2000 / Accepted: 17 July 2000     

Effects of territory quality, food availability and sibling competition on the fledging success of oystercatchers (Haematopus ostralegus)

We investigated the fledging probability of oystercatcher, Haematopus ostralegus, chicks as a function of hatching order, brood size, territory quality and food availability. Sibling dominance was related to the hatching order in both low- (’leapfrogs’) and high-quality (’residents’) territories. Differences in hatchling mass might have aided the establishment of a dominance hierarchy, since breeders produced small late eggs and hatchlings. These mass differences were most pronounced in leapfrogs, and in large broods in years with lower food availability (’poor’ years). Late hatchlings fledged less often and with lower body masses compared to early hatchlings in all situations. Leapfrogs produced smaller broods and hatched their broods more asynchronously in poor years than leapfrogs breeding in years with more available food (’good’ years) and residents breeding in both poor and good years. Large brood sizes resulted in lower survival of hatchlings in poor years. These results favour the ’brood reduction’ hypothesis. However, contrary to the expectations of this hypothesis, hatching order also affected fledging success in residents. Moreover, large brood size resulted in higher survival of hatchlings in good years, particularly in residents. Thus, although large broods experienced losses due to sibling competition in some years, they nevertheless consistently produced more fledglings per brood in all years, both as leapfrogs and residents. We believe this effect is due to parental quality correlating with initial brood size. Most leapfrogs, at best, fledged one chick successfully each year, losing chicks due to starvation. Nevertheless, leapfrog broods were reduced in size after hatching significantly less quickly than resident broods. These results suggest that breeders lay and hatch insurance eggs to compensate for unpredictable losses due to the high predation rates on both nests (ca 50%) and chicks (ca 90%), in accordance with the ’nest failure’ hypothesis. Received: 14 February 2000 / Revised: 27 September 2000 / Accepted: 10 June 2000     

Sibling aggression, hatching asynchrony, and nestling mortality in the black kite (Milvus migrans)

In siblicidal species, hatching asynchrony could act to reduce sibling rivalry or promote the death of last-hatched chicks. The pattern of hatching asynchrony was experimentally altered in the black kite Milvus migrans. Hatching asynchrony in control broods was intermediate between those of experimentally synchronised and asynchronised broods. Sibling aggression and wounds on the chicks were more commonly observed early in the nestling period and in synchronous nests. Serious injuries were observed on last-hatched chicks in asynchronous nests, as were observations of intimidated or crushed chicks. Sibling aggression was related to food abundance, but some chicks died at an early age in nests with abundant food (cainism). Cainism was more commonly found in asynchronous nests. For species with facultative siblicide, moderate hatching asynchrony could be a compromise between reducing sibling rivalry and avoiding large size differences between sibs that would result in cainism. Female black kites preferentially fed the smallest chicks and exhibited behaviours to reduce sibling aggression, contrary to observations in other siblicidal species. In a highly opportunistic forager such as the black kite, a strategy may exist to protract the life of all the chicks in the brood, waiting for unpredictable situations of food overabundance. This would induce the appearance of a parent-offspring conflict over brood reduction, reflected in the existence of a possible anticipated response by some of the chicks (cainism) and in the appearance of special behaviours by the parents to selectively feed smaller chicks or reduce sibling aggression. In this facultatively siblicidal species, cainism does not seem to be the final stage of an evolutionary trend favouring the raising of high-quality chicks, but a manifestation of a parent-offspring conflict over brood size. Received: 9 March 1998 / Accepted after revision: 8 August 1998     

Resource allocation varies with parental sex and brood size in the asynchronously hatching green-rumped parrotlet (<Emphasis Type="Italic">Forpus passerinus</Emphasis>)

When eggs hatch asynchronously, offspring arising from last-hatched eggs often exhibit a competitive disadvantage compared with their older, larger nestmates. Strong sibling competition might result in a pattern of resource allocation favoring larger nestlings, but active food allocation towards smaller offspring may compensate for the negative effects of asynchronous hatching. We examined patterns of resource allocation by green-rumped parrotlet parents to small and large broods under control and food-supplemented conditions. There was no difference between parents and among brood sizes in visit rate or number of feeds delivered, although females spent marginally more time in the nest than males. Both male and female parents preferentially fed offspring that had a higher begging effort than the remainder of the brood. Mean begging levels did not differ between small and large broods, but smaller offspring begged more than their older nestmates in large broods. Male parents fed small offspring less often in both brood sizes. Female parents fed offspring evenly in small broods, while in large broods they fed smaller offspring more frequently, with the exception of the very last hatched individual. These data suggest male parrotlets exhibit a feeding preference for larger offspring—possibly arising from the outcome of sibling competition—but that females practice active food allocation, particularly in larger brood sizes. These differential patterns of resource allocation between the sexes are consistent with other studies of parrots and may reflect some level of female compensation for the limitations imposed on smaller offspring by hatching asynchrony.     

The effect of queen-worker conflict on caste determination in the bumblebee Bombus terrestris

Endocrine analyses were used to investigate the well-known association between queen production and the onset of worker reproduction (termed the competition phase, CPh) in Bombus terrestris. Larvae that reached the age of 5 days before the CPh had a worker-like profile: low juvenile hormone (JH) biosynthesis rates and low JH hemolymph titers. In contrast, larvae that reached the age of 5 days during the CPh had a queen-like profile: high JH biosynthesis rates and high hemolymph JH levels. Larval fate could be manipulated by transplanting egg cells into host colonies with different social structures. There was a steep rise in JH production in larvae transplanted into colonies near or during the CPh. This indicates that during colony development, larvae switch from the ”worker developmental pathway” to the ”queen developmental pathway,” and that the switch is socially regulated. In small rearing groups, larvae reared with queens before the CPh developed into workers, whereas those reared with queens after the CPh developed into queens. Variation in worker type (naive or experienced) did not affect caste determination. Therefore, we hypothesize that queens produce a pheromone that directly inhibits queen differentiation by larvae. We also present two alternative scenarios that explain the timing of gyne production in B. terrestris, one based on ecological constraints and the other based on queen-worker competition. Received: 20 October 1999 / Received in revised form: 18 December 1999 / Accepted: 23 January 2000     

Call matching in the quacking frog (Crinia georgiana)

Males of the quacking frog Crinia georgiana produce calls consisting of 1–11 notes. Playback experiments using synthetic calls showed that males tend to match the number of notes in 2-note and 4-note stimuli; however, males tended to produce more than 1 note in response to a 1-note stimulus and fewer than 8 notes in response to an 8-note stimulus. Successive playbacks of two, 4-note calls from separate speakers indicate that males are likely to match the combined number of notes in the calls of two neighbors, even if they are not equidistant from the focal male. The results are compared with the few other studies of matching in anurans, and interpreted in terms of hypotheses developed to explain matching in songbirds. One attractive and testable hypothesis for call matching in C. georgiana is that males are attempting to produce calls that are at least as attractive to females as those of rivals, without wasting energy. Received: 14 February 2000 / Received in revised form: 11 April 2000 / Accepted: 3 May 2000     

Dispersal behaviour in a subsocial spider: group conflict and the effect of food availability

This study investigates proximate factors influencing dispersal behaviour in the subsocial spider Amaurobius ferox. Dispersal of spiderlings from the natal web occurred as a progressive sigmoidal function (mean duration of dispersal period=31 days), with considerable individual variability in developmental instar and body mass within the clutch at the time of dispersal. The spiderlings showed a significant decrease in group cohesion on the 6th day after their second moult, which corresponded to the beginning of the dispersal period. Mutual aggressiveness appeared when the spiderlings began to show predatory behaviour (4th day post-second moult) and increased over the course of the dispersal period. While lack of prey in the maternal nest accelerated dispersal behaviour, the addition of prey items lengthened the dispersal period in previously non-fed clutches. Individuals that dispersed were smaller than the remaining individuals when measured on the day 50% of the clutch had dispersed. Timing of the appearance of the developmental characters (second moult, predation activity, agonistic behaviour against siblings, reduction of group cohesion, dispersal) suggests that the dispersal trait might have evolved in consequence of these different functional behaviours. Received: 10 August 1999 / Received in revised form: 15 March 2000 / Accepted: 1 April 2000     

Testosterone and the allocation of reproductive effort in male house finches (Carpodacus mexicanus)

Testosterone has been proposed to serve as the mediator that controls the relative effort that an individual male bird will devote to mating effort versus parental effort. Here, we demonstrate a testosterone-influenced trade-off between parental and mating efforts in male house finches. Male house finches with experimentally elevated testosterone fed nestlings at a significantly lower rate, but sang at a higher rate than males without manipulated testosterone levels. Females mated to testosterone-implanted males fed nestlings at a significantly higher rate than females mated to males without testosterone implants, resulting in similar feeding rates for both treated and untreated pairs. The effects of testosterone on male house finches, however, were not as dramatic as the effects of testosterone observed in some other socially monogamous species of birds. Because extra-pair copulations are uncommon in house finches and males provide substantial amounts of parental care, these more modest effects may be due to differences in how the allocation of reproductive effort affects the costs and benefits of different reproductive behaviors. Received: 6 June 2000 / Accepted: 17 July 2000     

Correlations of food distribution and patch size with agonistic interactions in female vervets (Chlorocebus aethiops) and patas monkeys (Erythrocebus patas) living in simple habitats

Food distribution is hypothesized to be important in determining the nature of female relationships within social groups of primates. When food limits female reproductive success, spatially clumped foods are expected to produce strong, linear dominance hierarchies within groups, whereas more spatially dispersed foods are expected to produce weaker or non-existent dominance hierarchies. The association between food distribution and competitive relationships presumably occurs because clumped foods are usurpable but dispersed foods are not. We examined the spatial distribution of food patches (trees) and patch size relative to feeding behavior and agonistic interactions in vervets and patas monkeys, two closely related and sympatric species that nonetheless differ in the strength of the female dominance hierarchy. Food patches of both patas monkeys and vervets were small in size and randomly distributed in Acacia drepanolobium habitat. In contrast, in A. xanthophloea woodland, the habitat type that was exclusively used by vervets, food patches were larger and more spatially clumped. These similarities and differences between and within species were correlated with similarities and differences in the strength and linearity of their dominance hierarchies. Patas monkeys and vervets in A. drepanolobium habitat had dominance hierarchies that were weakly defined because there were relatively few agonistic interactions between females. By contrast, in A. xanthophloea habitat, vervets had a stronger, linear dominance hierarchy characterized by a higher rate of agonistic interactions over food. The covariation of agonistic interactions with patch size is discussed in relation to depletion time, another characteristic that may covary with food distribution, and resource renewal rate, an important determinant of agonistic interactions in insectivorous birds, fishes, insects, and mammals. Received: 18 February 2000 / Revised: 5 September 2000 / Accepted: 26 September 2000     

Intraspecific parasitism and split sex ratios in a monogynous and monandrous ant (Leptothorax nylanderi)

Sex ratios were bimodally distributed in a population of the monogynous and monandrous ant Leptothorax nylanderi during each of 3 study years. The population-wide investment ratios suggested worker control of sex allocation. Nest-level variation in the proportional investment in virgin queens was not affected by the presence or absence of a queen and only slightly by collecting year, but was correlated with nest size, total sexual investment and, unexpectedly, with differences in nestmate relatedness: small, low-investment nests and nests with several worker lineages produced male-biased sex ratios. Colonies containing several worker lineages arise from usurpation of mature colonies by unrelated founding queens and the fusion of unrelated colonies under strong nest site limitation. In contrast to facultatively polygynous and polyandrous species of social insects, where workers can maximize their inclusive fitness by adjusting sex ratios according to the degree of relatedness asymmetry, workers in mixed colonies of L. nylanderi do not benefit from manipulating sex allocation, as here relatedness asymmetries appear to be the same as in homogeneous colonies. Received: 7 December 1999 / Received in revised form: 29 February 2000 / Accepted: 13 March 2000     

Measurement of parental investment and sex allocation in the European beewolf Philanthus triangulum F. (Hymenoptera: Sphecidae)

Fisher’s 1930 theory of sex allocation predicts a population-wide 1:1 ratio of parental investment. We tested this prediction in the European beewolf, a sphecid wasp that hunts for honeybees as larval food. Because the method to quantify parental investment is of crucial importance, we compared the suitability of several different investment measures. Female/male cost ratios were determined from a sample and the total investment in sons and daughters was calculated. In addition, the actual number of prey items for sons and daughters was directly determined by excavating nests and counting the cuticle remains of the prey. Though mortality was high (70%), it had only a weak effect on the estimate of the investment ratio. Based on commonly used measures like fresh and dry weight of emerged adults, the investment ratio did not deviate from Fisher’s prediction of equal investment. However, progeny weight considerably underestimates investment in males and investment in large progeny. Measures that reflect the allocation of resources more directly (amount of provisions, brood cell volume) revealed a significant male bias and thus contradicted Fisher’s theory. Three kinds of explanation are discussed. First, non-adaptive explanations are unlikely. Second, from the spectrum of alternative adaptive theories, only models that assume a non-linear relationship between amount of investment and progeny fitness seem to be relevant for the study species. Third, though the number of prey in a brood cell seems to be a rather good measure of parental investment in European beewolves, some problems in measuring parental investment remain. These problems are of broad significance. Received: 17 June 1999 / Received in revised form: 6 July 1999 / Accepted: 11 July 1999     

Predatory behavior of crowned hawk-eagles (Stephanoaetus coronatus) in Kibale National Park, Uganda

Evaluating the nature and significance of predation on populations of wild primates has been difficult given a paucity of data regarding the phenomenon. Here we addressed this problem in a 37-month study of the predatory behavior of crowned hawk-eagles living at the Ngogo study site in Kibale National Park, Uganda. We collected prey remains underneath the nests of two pairs of eagles and census data on potential prey species to investigate prey selection and the ecological impact of predation on the Ngogo primate population. Results indicate that primates form the vast majority of all prey items. Eagles prey selectively on monkeys according to sex and species. Male primates were taken more often than females, while two species, redtail monkeys and mangabeys, were captured significantly more and less, respectively, than chance expectation. In addition, there was no bias in the age of prey: adult and non-adults were killed in numbers roughly equal to their proportional representations in the forest. Further analyses indicate that a non-trivial fraction of the entire primate population at Ngogo succumbs to crowned hawk-eagle predation each year. These results reveal both parallels and contrasts with those reported previously. Some of the parallels are due to similarities in prey availability, while contrasts are likely related to methodological differences between studies, inter- individual variations in predator hunting styles, and differences in prey abundance, demography, and behavior. Received: 29 March 2000 / Revised: 6 June 2000 / Accepted: 15 October 2000     

Effects of frequent mating on sex allocation in the simultaneously hermaphroditic great pond snail (Lymnaea stagnalis)

Simultaneous hermaphrodites have the opportunity to control the allocation of resources to the male and female function depending on the circumstances. Such flexibility also provides the possibility to influence sex allocation in the mating partner. To investigate this idea, we measured egg production (female investment) and sperm production as well as prostate gland size (both are part of male investment) under different mating regimes in the great pond snail Lymnaea stagnalis. We find no evidence for the prediction from sex allocation theory that sperm production increases with mating frequency. However, we do find that animals with more mating opporunities develop smaller prostate glands, in which seminal fluid is produced. Moreover, repeated mating increases egg production, thus shifting allocation towards the female function, and probably decreases growth. So, our data hint at a three-way trade-off between part of the male function (prostate gland), female function, and growth. Interestingly, sex allocation seems to be shifted in the opposite direction from the one predicted by theory. We discuss how this feminization is suggestive of a direct manipulation by the sperm donor, probably to stimulate immediate sperm use.     

Trade-off between fitness components in males of the polygynous butterfly Callophrys xami (Lycaenidae): the effect of multiple mating on longevity

The differential costs of mating paid by males and females influence the nature and strength of sexual selection. In butterflies, males invest a relatively large amount of time and resources in each mating, but male survival costs of mating have not been demonstrated. I present the results of experiments designed to measure the effect of different aspects of mating on male longevity in the polygynous butterfly Callophrys xami. In experiment 1, I compared the longevity of pairs of males that produced similar amounts of spermatophore, but that mated at different rates, a different numbers of times, and that produced spermatophores at different rates, and found that the longevity of ”low-mating-rate” males was not different from that of ”high-mating-rate” males. In experiment 2, the longevity of virgin males was not significantly different from that of multiply mated males. In experiment 3, I used resource-limited males resulting from experimental food limitation of last-instar larvae; resource-limited virgin males lived significantly more days than resource-limited multiply mated males. Since ecological costs of mating (e.g., disease transmission, predation risk) were excluded in the experiment, diminished male longevity was a product of physiological costs of sexual interactions. These results suggest that the cost of ejaculate production is an important cause of longevity reduction when there are resource limitations; however, the role of other possible physiological costs of mating in longevity reduction is still unknown. Received: 21 March 2000 / Accepted: 26 August 2000     

Female territoriality and the function of scent-marking in a monogamous antelope (Oreotragus oreotragus)

In monogamous species, females often choose between males according to the quality of the territories they defend, but the extent to which females themselves contribute to territory defence is frequently underestimated. Here we test for differences in male and female roles during paired scent-marking bouts, a key component of territorial defence, in a monogamous antelope. In two populations (Kenya, Zimbabwe) of klipspringer, Oreotragus oreotragus, both males and females usually scent-marked at the same site, but there were significant differences between sexes in terms of investment within bouts. Females initiated most bouts, thus dictating the marking strategy of the pair. Males initiated relatively few bouts, but deposited more scent marks per bout than females and were usually the last to scent-mark before leaving the site; they marked on the same branches as the female and thus overmarked her scent. Both sexes deposited more marks during paired than solo visits. Immediately preceding and following scent-marking bouts, males approached females and females left males more often than expected. Female scent-marking rates were higher when they were receptive than at other times, and this increase was matched by elevated marking rates of males. Females may increase marking rates when they are receptive in order to test the quality of their mate or to incite male competition. However, these ideas are unlikely to explain female scent-marking behaviour outside the mating season, which appears to be related primarily to territorial defence. We suggest that these differences in investment in scent-marking bouts are consistent with predictions that females may be autonomously territorial and that overmarking of female scent by males is a form of mate-guarding. Received: 17 November 1999 / Received in revised form: 24 February 2000 / Accepted: 13 March 2000     

Electrosensory prey detection in the African sharptooth catfish, Clarias gariepinus (Clariidae), of a weakly electric mormyrid fish, the bulldog (Marcusenius macrolepidotus)

During their seasonal runs in the Okavango and other freshwater bodies in southern Africa, the sharptooth catfish, Clarias gariepinus, specialises on the bulldog, Marcusenius macrolepidotus, as its main prey. We examined whether the catfish can locate bulldogs by detecting their pulse-type electric organ discharges (EODs). The electrosensory threshold for single-cycle, monopolar square-wave pulses was exceedingly low (down to 13 μV_p–p/cm for 4-ms pulses) in trained, food-rewarded sharptooth catfish (n=4), confirming the results of Lissmann and Machin who were, however, unable to identify a biological function. Other stimulus pulse waveforms (single-cycle, monopolar as well as bipolar sine-wave pulses) were also effective stimuli according to their spectral low-frequency energy contents (0– 30 Hz). Male bulldogs display an EOD pulse approximately 10× the duration of female EODs (≈0.5 ms). The C. gariepinus threshold for field-recorded playbacks of a male bulldog EOD (of long duration) was 103 μV_p–p/cm, whereas the brief female and juvenile EODs were not detected (using intensities of natural EODs). EODs of other mormyrids were detected when either monopolar or of long duration. Signal source amplitude increased linearly with standard length (SL) in bulldogs. Signal reach, as calculated from signal source amplitude and receiver sensitivity, is up to 150 cm for a large male bulldog (SL 27.5 cm), and 83 cm for a male that has just turned sexually mature (SL 12.6 cm). Therefore, most bulldogs eaten by catfish are probably male, in agreement with the size distribution of bulldogs found in catfish stomachs. These results suggest that sharptooth catfish rely heavily on their acute electrical sense during hunting, and an important function for electroreception in an African catfish has been identified. Received: 13 December 1999 / Revised: 20 April 2000 / Accepted: 20 May 2000     

Dynamics of pheromone production and communication in the mountain pine beetle, Dendroctonus ponderosae Hopkins, and the pine engraver, Ips pini (Say) (Coleoptera: Scolytidae)

Summary. The mountain pine beetle, Dendroctonus ponderosae Hopkins, and the pine engraver, Ips pini (Say), often co-exist in lodgepole pine, Pinus contorta var. latifolia Engelmann. Intra- and interspecific semiochemical communication occurs in both species and their complete semiochemical repertoire and precise dynamics of pheromone production have not been elucidated. Porapak-Q extracts of captured volatiles from beetles of each species aerated at different attack phases (freshly emerged, pioneer sex alone in the log and both sexes paired in new galleries), followed by gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectroscopic analyses identified 17 compounds (seven compounds common to both species, six present in D. ponderosae and four present in I. pini) that excited the antennae of either or both species. Seven compounds for D. ponderosae and nine for I. pini had not been assessed for behavioural activity. In field trapping experiments, 2-phenylethanol produced by both species inhibited the response of D. ponderosae to its aggregation pheromones. exo- and endo-Brevicomin produced by D. ponderosae significantly decreased the response of I. pini to its aggregation pheromone ipsdienol. Nonanal, a ubiquitous compound found in the volatiles of lodgepole pine, various nonhosts and in both beetle species deterred the response of I. pini to ipsdienol. The occurrence of cis-verbenol, trans-verbenol and verbenone in emergent I. pini, and verbenone and 2-phenylethanol in emergent D. ponderosae suggests that these compounds may inhibit aggregation and induce dispersal following emergence. Termination of aggregation in D. ponderosae appears to depend on the production of frontalin in combination with changes in the relative ratios of verbenone, exo-brevicomin, trans-verbenol and 2-phenylethanol. In I. pini, the cessation of ipsdienol production by males is probably the main factor in terminating aggregation. Received 16 November 1999; accepted 7 August 2000     

Lack of detectable nepotism in multiple-queen colonies of the fire ant Solenopsis invicta (Hymenoptera: Formicidae)

Multiple-queen (polygyne) colonies of the introduced fire ant Solenopsis invicta present a paradox for kin selection theory. Egg-laying queens within these societies are, on average, unrelated to one another, and the numbers of queens per colony are high, so that workers appear to raise new sexuals that are no more closely related to them than are random individuals in the population. This paradox could be resolved if workers discriminate between related and unrelated nestmate sexuals in important fitness-related contexts. This study examines the possibility of such nepotism using methods that combine the following features: (1) multiple relevant behavioral assays, (2) colonies with an unmanipulated family structure, (3) multiple genetic markers with no known phenotypic effects, and (4) a statistical technique for distinguishing between nepotism and potentially confounding phenomena. We estimated relatedness between interactants in polygyne S. invicta colonies in two situations, workers tending egg-laying queens and workers feeding maturing winged queens. In neither case did we detect a significant positive value of relatedness that would implicate nepotism. We argue that the non-nepotistic strategies displayed by these ants reflect historical selection pressures experienced by native populations, in which nestmate queens are highly related to one another. The markedly different genetic structure in native populations may favor the operation of stronger higher-level selection that effectively opposes weaker individual-level selection for nepotistic interactions within nests. Received: 28 June 1996 / Accepted after revision: 6 October 1996     

Molecular genetic and behavioral analysis of social organization in the Asian elephant (Elephas maximus)

We report on the genetic evaluation and behavioral study of social organization in the Asian elephant (Elephas maximus). Although Asian elephants and African elephants (Loxodonta africana) were previously thought to have similar social organizations, our results demonstrate a substantial difference in the complexity and structure of Asian elephant social groupings from that described for African savanna elephants. Photographic cataloging of individuals, radio telemetry, and behavioral observations in Ruhuna National Park, Sri Lanka, enabled us to assign associated females and young to four groups with overlapping ranges. Genetic sampling of individuals from the four groups in Ruhuna National Park and three other groups in surrounding areas, conducted through PCR amplification and sequencing of mitochondrial DNA from dung, supported the matriarchal nature of female groups and the lack of inter-group transfer of females. Behaviorally and genetically, the identified social groups were best described as ”family groups”. We did not find any evidence for the existence of social groups of higher complexity than family groups. Received: 25 March 2000 / Received in revised form: 28 March 2000 / Accepted: 1 April 2000     

The feeding behaviour of Schistocerca gregaria,the desert locust,on two starch mutants of Arabidopsis thaliana

Summary. Schistocerca gregaria, the desert locust, has been shown to regulate its dietary intake with respect to specific macronutrients in synthetic foods. This study examined the nutrients in the leaves of two starch mutants of Arabidopsis thaliana, and then compared the feeding behaviour of locusts on the two starch mutants. The high-starch mutant had c. 25 times more starch than the no-starch mutant. Newly molted 5th stadium locusts were preconditioned for 3 days on one of the mutants, and then observed for 90 min while exposed to the same or the alternative mutant. Locusts pretreated with the no-starch mutant fed longer during the first meal on high-starch mutants, spent more time feeding, and had the smaller latency to begin a meal when compared to the locusts pretreated on the high-starch mutant. The results of the study are interpreted in light of an integrative model of nutrient balancing. Received 16 November 1999; accepted 23 December 1999