Why does the herring gull lay three eggs?

Food supplements placed daily beside the nests of herring gulls, Larus argentatus, for the first 5 days after the first chick hatched produced improved weight gains over this initial period and higher fledging success, particularly in the third chick. The fledging success of the fed group appears to be due to increased weight gain and not to increased parental protection in the supplemented period. Since there is indirect evidence that food is available this suggests that the parents are putting less effort into foraging for their chicks than they are able to, and less than is in the interests of the third chick, in the first days after hatching. On a separate colony we found that having three chicks in the brood for more than 5 days resulted in lower weight gains for the second chick, but not the first. We suggest that fledging three chicks rather than one or two greatly increases the parents' reproductive effort, and consequently interpret the third egg as primarily insurance against the loss of the first or second.     

Treatment of established postoperative nausea and vomiting: a quantitative systematic review

Background  

The relative efficacy of antiemetics for the treatment of postoperative nausea and vomiting (PONV) is poorly understood.     

Taking sociality seriously: the structure of multi-dimensional social networks as a source of information for individuals

Understanding human cognitive evolution, and that of the other primates, means taking sociality very seriously. For humans, this requires the recognition of the sociocultural and historical means by which human minds and selves are constructed, and how this gives rise to the reflexivity and ability to respond to novelty that characterize our species. For other, non-linguistic, primates we can answer some interesting questions by viewing social life as a feedback process, drawing on cybernetics and systems approaches and using social network neo-theory to test these ideas. Specifically, we show how social networks can be formalized as multi-dimensional objects, and use entropy measures to assess how networks respond to perturbation. We use simulations and natural 'knock-outs' in a free-ranging baboon troop to demonstrate that changes in interactions after social perturbations lead to a more certain social network, in which the outcomes of interactions are easier for members to predict. This new formalization of social networks provides a framework within which to predict network dynamics and evolution, helps us highlight how human and non-human social networks differ and has implications for theories of cognitive evolution.     

Some observations on the effect of Daflon (micronized purified flavonoid fraction of Rutaceae aurantiae) in bancroftian filarial lymphoedema

BACKGROUND: Morbidity management is a core component of the global programme for the elimination of lymphatic filariasis. In a double-blind clinical trial, the tolerability and efficacy of Daflon (500 mg) + DEC (25 mg) or DEC (25 mg) alone, twice daily for 90 days, was studied in 26 patients with bancroftian filarial lymphoedema. RESULTS: None of the patients in either drug group reported any adverse reaction throughout the treatment period (90 days). Haematological and biochemical parameters were within normal limits and there was no significant difference between the pre-treatment (day 0) and post-treatment (day 90) values. The group receiving Daflon showed significant reduction in oedema volume from day 90 (140.6 PlusMinus; 18.8 ml) to day 360 (71.8 PlusMinus; 20.7 ml) compared to the pre-treatment (day 0, 198.4 PlusMinus; 16.5 ml) value. This accounted for a 63.8% reduction in oedema volume by day 360 (considering the pre-treatment (day 0) as 100%). In the DEC group, the changes in oedema volume (between day 1 and day 360) were not significant when compared to the pre-treatment (day 0) value. The percentage reduction at day 360 was only 9%, which was not significant (P > 0.05). CONCLUSION: This study has shown that Daflon (500 mg, twice a day for 90 days) is both safe and efficacious in reducing oedema volume in bancroftian filarial lymphoedema. Further clinical trials are essential for strengthening the evidence base on the role of this drug in the morbidity management of lymphatic filariasis.     

Consortship and Mating Success in Chacma Baboons (Papio cynocephalus ursinus)

Chacma baboons (Papio cynocephalus ursinus) show a lower consortship take‐over rate and longer consortship duration than the other savannah baboons ( Bulger 1993 ). It has been argued that researchers have focused on atypically small troops with few adult males, resulting in low competition for access to oestrous females. Consortship data from two mountain baboon troops containing seven and four males, respectively, were analysed to determine whether the troop with the greater number of males showed a weaker correlation between mating success and rank due to an expected higher consortship take‐over rate. No consort take‐overs were observed in either study troop and mating success in both troops was correlated strongly with male rank. The distribution of days spent in consortship amongst the males could be explained by the priority‐of‐access‐model. The degree of cycle overlap determined the number of males observed consorting oestrous females, whereas the number of males did not influence the relationship between rank and consorting activity.     

Are Baboon Infants Sir Phillip Sydney's Offspring?

Data on mother-offspring interactions in chacma baboons ( Papio cynocephalus ursinus ) were used to test predictions arising from Bateson's (1994) dynamic assessment model of mammalian weaning conflicts. The results provide preliminary support for this model. Infants, rather than mothers, controlled the amount of investment received in the early postnatal period and infants were motivated to begin foraging in the absence of maternal rejection. Furthermore, seven out of 10 infants did not display any tantrum behaviour during observations throughout the first year of life. Only those infants considered to be vulnerable to a seasonal reduction in weaning foods displayed high level tantrum behaviour that was accompanied by an increase in the amount of investment received from their mothers. Habitat quality is suggested to be critical in determining the success of a transition to independent foraging both within and between habitats, with mothers being sensitive to this and responding appropriately to infants who require increased investment. The high intensity tantrum behaviour is necessary to convey unambiguous information to a mother with imperfect knowledge of the offspring's state, and to convey the urgency of need, enabling infants to break into maternal schedules.     

Indices of environmental temperatures for primates in open habitats

Studies of thermoregulation in primates are under-represented in the literature, although there is sufficient evidence to suggest that temperature represents an important ecological constraint. One of the problems in examining thermoregulation in primates, however, is the difficulty in quantifying the thermal environment, since shade temperatures, solar radiation, humidity and wind speed all serve to alter an animals perceived temperature. Since animals respond to their perceived temperature, we need methods to account for each of these factors, both individually and collectively, if we are to understand the integrated impact of the thermal environment on primates. Here, we present a review of some thermal indices currently available. Black bulb temperatures can account for the effect of solar radiation, with wind chill equivalent temperatures and the heat index providing quantifiable estimates of the relative impact of wind speed and humidity, respectively. We present three potential indices of the perceived environmental temperature (PET) that account for the combined impact of solar radiation, humidity and wind speed on temperature, and perform a preliminary test of all of the climatic indices against behavioural data from a field study of chacma baboons (Papio cynocephalus ursinus) at De Hoop Nature Reserve, South Africa. One measure of the perceived environmental temperature, PET2, is an effective thermal index, since it enters the models for feeding and resting behaviour, and also accounts for levels of allogrooming. Solar radiation intensity is an important factor underlying these relationships, although the wind chill equivalent temperature and humidity enter the models for other behaviours. Future studies should thus be mindful of the impact of each of these elements of the thermal environment. A detailed understanding of primate thermoregulation will only come with the development of biophysical models of the thermal characteristics of the species and its environment. Until such developments, however, the indices presented here should permit a more detailed examination of the thermal environment, allowing thermoregulation to be given greater precedence in future studies of primate behaviour.