The benefits to captive animals of environmental enrichment (EE) are widely recognized. Few studies have, however, studied how to maximise the effect of EE. One issue with EE programs seems to be habituation to the enrichment device. To study the effect of habituation to EE, 14 captive sloth bears (Melursus ursinus) were subjected to two different EE treatments. Treatment one presented EE (logs with honey containing holes) for five consecutive days, whereas treatment two presented EE on intermittent days for five days. Intermittent presentations tended to reduce habituation toward the EE. Both consecutive and intermittent presentations significantly reduced stereotypies; however, the consecutive presentations had a longer-lasting effect. Explorative behaviors increased in both treatments, consistent with earlier findings that EE increase levels of natural behaviors. Other behaviors were unaffected by the EE presentations. The results show that intermittent presentation of EE objects may secure the interest of the animals, but continuous access to enrichment may be more efficient in reducing stereotypies in the long run.

A number of studies have investigated anticipatory behaviour in animals as a measure of sensitivity to reward or as an expression of emotional state. A common feature of many studies is that they base inferences on seemingly arbitrary measures, for example, the frequency of behavioural transitions (ie number of times an animal switches between different behaviours). This paper critically reviews the literature and discusses various hypotheses for why specific behavioural responses occur in the anticipatory period between the signal and reward in conditioned animals. We argue that the specific behaviours shown may be the result of superstitious learning and thus highly variable, leaving behavioural transitions as the only response that can be scored consistently, and that sometimes these responses may relate more to frustration than to a positive emotional state. Finally, we propose new research approaches to avoid potential confounds and improve future studies on this topic.

Observations of play in animals have been suggested as a promising indicator of positive emotions and thus of positive animal welfare. However, if play can follow the proposed reward cycle concept where animals estimate and value reward differently in different phases of the cycle (anticipation, consummation and post-consummation) is unclear. To investigate if a reward cycle for play exists in growing pigs, we carried out an exploratory study where pigs were tested when they were naïve to a reward cycle test (first occasion) against when they were accustomed to going through the test after having the access to an open play arena with objects. Forty undocked pigs were housed in a weaner stable with two castrated males and two females per pen. Within each litter, we randomly selected and tested one male and one female test pig, each being tested as naïve or accustomed to the testing environment. The first week the pigs (n = 20) were tested four times and regarded as naïve during the first day. After that they were regarded as accustomed, and were tested twice a week for 3 weeks. We observed the behavior of the tested pairs in three subsequent stages: (1) in a holding pen 3 min, (2) in a play arena 15 min, and (3) in their home pen 10 min. When accustomed, pigs showed more locomotor play, social interactions and standing, and a tendency of more orientation toward the play arena and exploring bars facing the play arena (i.e., reward-seeking behavior) in the holding pen than when they were naïve, suggesting an anticipation to enter the play arena. Performing high numbers of object play in all sessions, and for accustomed pigs more exploration and social interaction, but less locomotor play and walking in the play arena may suggest consumption of play and exploration. Finding more lying and sitting in accustomed pigs, but less standing and walking in the home pen is in line with the previous hypothesis of the post-consummatory behaviors. Our study showed mixed results for the existence of a reward cycle for play in pigs and generated questions for future research.