Influences of food type on food-carrying behavior in rats (Rattus norvegicus).

It is known that rats tend to eat a smaller/lighter piece of food at the food source but carry a larger/heavier one to the nest for consumption. This could be interpreted well in terms of the trade-off or motivational conflict between "feeding" and "risk avoidance", because eating food immediately satisfies feeding motivation while carrying food has an advantage to avoid predatory risk by keeping time spent outside the nest shorter. In the present study, influences of incentive factors of feeding motivation on food-carrying behavior were evaluated using three different kinds of food that were identical in weight.

Use of a standard strain for external calibration in behavioral phenotyping.

The present paper evaluates the inclusion of a standard strain or outbred stock in multi-strain behavioral phenotyping protocols to perform the same role as the external standard in biochemical assay procedures. As potential standards, the F344 inbred strain and an outbred stock of Long Evans were tested with three other inbred strains. To evaluate the influence of rearing conditions on phenotype stability, one group of F344s was born at the University of Tsukuba, another, bred elsewhere and delivered to Tsukuba at 4 weeks of age.

Food-carrying behavior increased under risk-approaching signal in rats (Rattus norvegicus).

Food-carrying behavior in foraging rats has been assumed to have an advantage to avoid risks by shortening time spent outside their nests. However, there is no experimental evidence for this. In the present study, food-carrying behavior for four sizes of food pellets (45, 100, 200, and 1000 mg) was measured under the presentation of risk-approaching signal (shock-conditioned tone) to verify whether food-carrying behavior is related to risk avoidance or not.