Effects of thermoregulation on human sleep patterns: A mathematical model of sleep-wake cycles with REM-NREM subcircuit

In this paper we construct a mathematical model of human sleep/wake regulation with thermoregulation and temperature e ects. Simulations of this model show features previously presented in experimental data such as elongation of duration and number of REM bouts across the night as well as the appearance of awakenings due to deviations in body temperature from thermoneutrality. This model helps to demonstrate the importance of temperature in the sleep cycle. Further modi cations of the model to include more temperature e ects on other aspects of sleep regulation such as sleep and REM latency are discussedPostprint (author's final draft

Processes of behavioural timing and their implications for foraging theory

SIGLEAvailable from British Library Document Supply Centre-DSC:D191658 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Predicting body temperature of endotherms during shuttling

This paper presents two models that can be used to predict the temporal dynamics of body temperature in endotherms. A first-order model is based on the assumption that body temperature is uniform at all times, while a second-order model is based on the assumption that animals can be divided in a core and a shell, the temperature being uniform within each compartment. According to the second-order model, animals may be able to maintain their internal organs at almost constant temperature during shuttling despite large variations in the temperature of peripheral tissues. [KEYWORDS: Core-shell models; Second-order models; Octodon degus; Patch use]

Hiding from swans: optimal burial depth of sago pondweed tubers foraged by Bewick's swans

1 We used a combination of laboratory and field experiments to test the hypothesis that the burial depth of Potamogeton pectinatus tubers will vary with local sediment type and swan predation pressure. 2 In the field, mortality due to predation by swans decreased linearly with burial depth (from 100 at the surface to 55 at 225 mm depth) and with sediment clay content. Average tuber size showed an eightfold increase when burial depth increased from 25 to 275 mm. 3 A laboratory experiment showed that plant emergence in spring decreased with increasing planting depth and with decreasing tuber size. 4 An optimization model combining these empirical results showed that optimal tuber survival is achieved if tuber size and burial depth increases as swan predation pressure rises. The model predicted different optimal combinations of tuber size and burial depth for sandy and clay-rich sediments. 5 A common-garden experiment showed that plants grown from large tubers produce larger tubers. Significant clonal variation in tuber size was also detected: after standardizing for tuber production, plants originating from sandy sites produced larger tubers than those originating from clay-rich sites. 6 Our results suggest the existence of spatial refuges for pondweed tubers against swan predation

Feeding experience and relative size modify the begging strategies of nestlings

The offspring of birds and mammals use a combination of movements and vocalizations, known as begging, to solicit food from their parents. A widespread interpretation of begging is that it constitutes an honest signal of offspring need. But we know that in the house sparrow (Passer domesticus) the intensity of begging calls reflects the past experience of offspring in addition to their need. Here we show that this result generalizes to other species. An experiment with hand-reared magpies (Pica pica) and great spotted cuckoos (Clamator glandarius) indicates that the begging strategies depend on the past experience of chicks and the composition of their brood. In asynchronous two-magpie broods, both chicks begged at the same intensity when the large chick obtained food more easily than its sibling, but the large chick begged at higher intensity when it was easier for the smaller chick to obtain food. Cuckoo chicks begged at higher intensity than magpies. [KEYWORDS: begging, communication, handicap principle, hatching asynchrony, learning, signaling of need.]

Reciprocity and conditional cooperation between great tit parents

When individuals invest in a common good, an efficient outcome is hard to achieve, because each can free ride on others’ efforts. This problem can lead parents that raise their young together to reduce their investment in care, with negative consequences for offspring. Here, we present a mathematical model to show that a strategy of conditional cooperation, in which parents take turns feeding their young, can resolve this problem. To test this idea, we studied the behaviour of great tit parents raising chicks together. We found that parents speed up their feeding rate after their partner has visited the chicks, but slow down again once they have visited in turn, promoting alternation. We conclude that conflict over parental investment in this species is partly ameliorated by a simple form of reciprocity