Abstract: It has been proposed that use of socially acquired information by animals should increase as the time available for individual resource sampling decreases. We gave Norway rat “observers” either 2 or 5 h day-1 to sample four foods. Three of these foods were relatively palatable, but protein-poor; the fourth was relatively unpalatable, but protein-rich. We found that observer rats that for 2 h day-1 both sampled foods and interacted with demonstrators eating only the protein-rich food ate more of the protein-rich food than did observers that sampled for 2 h day-1 but had no opportunity to interact with demonstrators. On the other hand, observer rats that could sample foods for 5 h day-1 ate equal amounts of protein-rich food whether they interacted with a demonstrator fed protein-rich food or not. Subsequent analyses showed that the time available to observers to sample foods, rather than the opportunity to interact with demonstrators determined whether such interaction influenced observers' food choices. The results are consistent with the hypothesis that animals increase their use of public information in response to temporal constraints on opportunities for resource sampling.

Abstract: When birds raised by another species become adults, they (if they are non-brood-parasitic species) usually attempt to mate with birds of their foster species rather than with birds of their own species, a phenomenon called sexual imprinting. Avian brood parasites lay their eggs in nests of other species (the hosts) that rear the young, but the problem of sexual imprinting among brood parasites has generally been neglected, and brood parasites have been considered as an exception among birds. Here, we show, with data from field observations and field experiments, firstly, that adult great spotted cuckoos Clamator glandarius sometimes maintain contact with both older nestling and fledgling cuckoos. Adult cuckoos visited parasitized nests during the last days of the nestling period (5 observations) and, when parasitic chicks left the nest, adult cuckoos maintained contact with the young (14 observations). Adults and fledgling cuckoos communicated vocally (5 observations), and an adult great spotted cuckoo even fed a parasite fledgling in two cases. Secondly, when experimentally cross-fostered in nests of magpie Pica pica hosts outside the parasite breeding range (thus avoiding visual and acoustic communication with adult cuckoos), young cuckoos did not learn to recognize their own species when only one cuckoo chick was introduced per nest, but they learnt to recognize conspecifics when two cuckoos were reared together. This means that young great spotted cuckoos apparently must learn to recognize conspecifics, that is, recognition is not innate. Social interactions between adult brood parasites and young have also been reported in other brood parasites; thus, brood parasites are probably not an exception to the general phenomenon of imprinting, and young brood parasites may need to be imprinted on conspecifics, although more studies on other brood parasite species are needed to confirm this.

Abstract: In a number of mammalian species, males appear to have superior spatial abilities to females. The favoured explanations for this cognitive difference are hormonal, with higher testosterone levels in males than females leading to better spatial performance, and evolutionary, where sexual selection has favoured males with increased spatial abilities for either better navigational skills in hunting or to enable an increased territory size. However, an alternative explanation for this sex difference focuses on the role of varying levels of oestrogen in females in spatial cognition (the 'fertility and parental care' hypothesis). One possibility is that varying oestrogen levels result in variation in spatial learning and memory so that, when tested across the oestrous cycle, females perform as well as males on days of low oestrogen but more poorly on days of high oestrogen. If day in the oestrous cycle is not taken into account then, across an experiment, any sex differences found would always produce male superiority. We used a spatial working memory task in a Morris water maze to test the spatial learning and memory abilities of male and female rats. The rats were tested across a number of consecutive days during which the females went through four oestrous cycles. We found no overall sex differences in latencies to reach a submerged platform in a Morris water maze but, on the day of oestrus (low oestrogen), females took an extra swim to learn the platform's location (a 100% increase over the other days in the cycle). Female swim speed also varied across the oestrous cycle but females were no less active on the day of oestrus. These results oppose the predictions of the fertility and parental care hypothesis.