Abstract: We examined whether very young dairy calves are able to discriminate between two people, and whether they use the colour of clothing or other indices to do so. During the familiarisation phase, one person (the familiar rewarder), who always wore the same colour clothes, gave milk, spoke gently and patted the calves in their individual pen for 6 days each week. During the test phase, the calf had to make a choice in an Y-maze placed in front of the gate of its stall. When the calves chose the familiar rewarder, they received 200 ml of milk as reinforcement. When they made the incorrect choice, they received nothing and were returned to their stall. On each test day, the calves made eight choices. The criterion of success was that the calf made at least six correct choices in eight trials on each of two consecutive test days (P<0.021 by the binomial law). The first experiment was carried out with fourteen 1-week-old male and female Holstein calves to see if calves could approach a person, who changed position in the maze, in order to obtain a feed reward. The familiar rewarder wore the same clothes as during the period of familiarisation and was in one arm of the Y-maze. The other arm was empty and the position of the familiar rewarder in the maze was randomised. Eleven of the 14 calves reached the criterion for success, after only three tests. The second experiment, carried out with five 2-week-old calves, examined whether the calves can differentiate the familiar rewarder (wearing the same clothing as during the period of familiarisation) from another person (the non-rewarder) wearing clothes of a different colour. The criterion of success was reached by all five calves. The third experiment was carried out with seven 2-week-old calves. It examined whether the calves can differentiate the familiar rewarder and the non-rewarder, when the two people are wearing clothes of the same colour (i.e. the same colour worn by the familiar rewarder during the phase of familiarisation). None of the calves were able to reach the criterion of success within a limited number of four test days. Often, calves would always choose the same arm of the maze. The fourth experiment was carried out on six 1-month-old calves. It was similar to experiment 3 with the difference that the familiar rewarder and the non-rewarder both wore the same colour clothes, but which were not the same colour as worn during the phase of familiarisation. Only one calf achieved the criterion of success within two test days. Results demonstrated that colour cues help very young calves to discriminate between two people, when these people wear different colour clothing. Some calves may be able to use other indicators than the colour of clothing. The Y-maze method is an promising way of examining calves' abilities to recognise people.

Abstract: Four Arabian horses and one Thoroughbred were presented with a series of two-choice color vs. gray discrimination problems. Testing was done in a stall containing a wall with two translucent panels that were illuminated from behind by light projected through color or gray filters to provide the discriminative stimuli. Horses first learned to push one of the panels in order to receive the food reward behind the positive stimulus in an achromatic light-dark discrimination task, and were then tested on their ability to discriminate between gray and four individual colors: red (617 nm), yellow (581 nm), green (538 nm), and blue (470 nm). The criterion for learning was set at 85% correct responses, and final testing for all color vs. gray discriminations involved grays of varying intensities, making brightness an irrelevant cue. Three subjects were tested with all four colors. Two of those subjects successfully reached the criterion for learning on all four color vs. gray discriminations, while the third reached criterion with red and blue, but performed at chance levels for yellow and green. A fourth horse was only tested with green and yellow, and a fifth only with blue, and both of those horses successfully reached criterion on the discriminations they attempted. With the exception of the one subject's poor performance with yellow and green, there was no significant difference between horses on any of the discrimination tasks, and no significant difference in their performance with different colors. The results suggest that horses have color vision that is at least dichromatic, although partial color-blindness may occur in some individuals.

Abstract: Learning and memory abilities of 1-3 year old horses were assessed using instrumental and spatial tasks. No important differences were observed in the success of learning of the instrumental task (chest opening) according to sex or age. Younger females, however, seemed to learn more quickly. The offspring of a particular stallion were slower to learn than other horses. All horses memorised this task and opened the chest in a very short time in the second session. The animals that learned the task easily were not necessarily faster in the memorisation test. In the spatial task, learning ability did not seem to be related to age but more females than males were successful. The offspring of one stallion were more successful than other horses. Only 76% of the horses succeeded in the memorisation test, independently of age or sex. No correlation was found between the tasks in the latencies of either the learning or the memorisation tests for the same horses. The instrumental and spatial tasks may involve different processes.

Abstract: For red deer stags, fighting both has appreciable costs and yields considerable benefits. Up to 6% of rutting stags are permanently injured each year, while fighting success and reproductive success are closely related, within age groups as well as across them. Fighting behaviour is sensitive to changes in the potential benefits of fighting: stags fight most frequently and most intensely where potential benefits are high and tend to avoid fighting with individuals they are unlikely to beat. The relevance of these findings to theoretical models of fighting behaviour is discussed.