Institute of Animal Welfare and Behaviour, Veterinary Department, Berlin, Germany
The problem-solving abilities of Labrador Retrievers at 2 different life stages were taken into account. The dogs had to solve 2 test sequences of 5 hidden food/ toy tasks. The development of behaviour patterns between the end of the weaning and socialisation phase were assessed. 25 Puppies at their 8th and 16th week of life from 5 litters took part. The food was hidden by diverse objects: under a wheeled wooden board, a pylon, a "Knepig"TM, behind chairs and in the hand of the experimenter. The puppies had to find out by their own, how they could reach it in 4 trials. The tests were videotaped and analysed frame-by-frame. The main documented parameters were coping strategies, e.g. licking or yawning, the latency of reaching the food as well as the strategies which the dogs used to solve the hidden food task. The frequency and duration of these parameters were analysed. The puppies at the age of 8 weeks have shown the tendency of fewer problem-solving strategies. The average latency of reaching the food in the 4 trials of the test with the wooden board improved with each attempt. The dogs were not necessarily faster in the 4th trial. Thus, the correlation between the mean time of reaching the food and the trial number was negative or positive for all 5 tests; but just for the wheeled wooden board test significant (Spearman, p= -0.9, P<0.000). The problem-solving strategies in the 8th and 16th week were tendential equal, but the older puppies have shown behaviour patterns characterised by more persistence. Dogs which mainly reached the food through a problem-solving strategy also preferred these behaviour patterns at the age of 16 weeks. Licking intentions and yawning etc. were behaviours which were assessed with a huge individual diversity. When the dogs solved the task in the 1st or 2nd attempt, the object which hid the food was fixed more. Thus, the correlation between the mean time of reaching the food and the trial number was sometimes negative or positive.
Dogs of the same litter have mainly borne resemblance in the behaviour patterns while the comparison of dogs of different litters has revealed a huge diversity. This diversity was mainly assessed for motivation and problem-solving abilities as well as for displacement activities. The motivation problems of the puppies at the age of 8 weeks led to the assessment that behavioural tests of dogs have to begin later at the end of the socialisation phase.