Elevation-related difference in serial reversal learning ability in a nonscatter hoarding passerine

Abstract

Environments characterized by scarce and variable food supply, termed "harsh environments," have been hypothesized to favor cognitive abilities that aid an animal in finding food, remembering where it is located, or predicting its availability. Most studies of the "harsh environment" hypothesis have found that scatter hoarders from harsher environments have better spatial memory abilities, but few studies have looked at this hypothesis in nonscatter hoarders. Here, we present the first comparison of performance on a serial reversal learning task in a nonscatter hoarder from 2 elevations that differ in harshness. Serial reversal learning tasks measure a suite of cognitive abilities that are believed to allow an animal to adjust its foraging behavior to match changes in the availability of food over time. Therefore, performance on this task is predicted to increase with elevation. There was no significant difference between the high and low elevation great tits in initial reversal learning accuracy. While both high and low elevation birds were able to improve their reversal learning accuracy, they did not differ in their rate of improvement over reversals. However, we found that lower elevation birds had higher accuracy across all reversals. Contrary to the "harsh environment" hypothesis, our findings suggest that birds from the less harsh environment at low elevation performed more accurately on the reversal learning task. Overall, our results suggest that the study of the relationship between harshness and cognition in nonhoarders would benefit from taking into account other environmental factors, and trade-offs with other cognitive abilities.

An intraspecific appraisal of the social intelligence hypothesis

“…[ 63 ] P. gambelli spatial memory, reversal learning altitude mixed (no effect and negative) not tested Hermer et al . [ 64 ] great tit, Parus major reversal learning altitude mixed (no effect and negative) not tested …”

Great tits who remember more accurately have difficulty forgetting, but variation is not driven by environmental harshness

“…Instead, and in accordance with a lack of spatial memory accuracy differences, we found no difference between high and low elevation birds in their proactive interference. Interestingly, in a previous study on great tits collected from the same population, we found that birds from high elevation performed less accurately on a serial spatial reversal learning task than low elevation great tits 16 . We surmised that one potential explanation for this result was that spatial memory may have been more accurate in high elevation great tits, which would lead to greater spatial proactive interference and worse reversal performance, as found in the scatter hoarding system 21 , 41 .…”

“…A first possible explanation is that the two elevations we sampled do not differ enough in harshness. However, this is unlikely as previous studies that sampled birds from the same population and elevations found a significant cognitive difference (i.e., laboratory test of serial reversal learning 16 ), as well as differences in breeding phenology 52 and parental care 45 between high and low elevation birds. Therefore, some environmental difference between high and low elevations seems to be driving behavioural differences.…”

“…In this study, we compared the performance of non-scatter hoarding, great tits ( Parus major ), that feed on patches of seeds during the winter 44 , from several high and low elevation sites that differ in harshness 16 , 45 , 46 on a spatial memory task and a single spatial reversal task designed to measure proactive interference 21 (Fig. 1 b).…”

Chimpanzees use advanced spatial cognition to plan least-cost routes

“…There is growing evidence to support this from comparative studies of primates (review in Rosati, 2017), birds (Freas et al, 2012, Sonnenberg et al, 2019, bats and rodents (review in Harvey and Krebs, 1990). However, a recent study highlighted the need for a clearer definition of what constitutes environmental 'harshness' (Hermer et al, 2018). Based on the results of this study, we propose that environmental harshness could be expanded beyond the spatio-temporal complexity of food resources to include landscape complexity.…”