Cache spacing patterns and reciprocal cache theft in New Zealand robins

Intra-individual variation in performance on novel variants of similar tasks influences single factor explanations of general cognitive processes

Intra-individual variation in performance within and across cognitive domains may confound interpretations of both domain-general and domain-specific abilities. Such variation is rarely considered in animal test batteries. We investigate individual consistency in performance by presenting pheasant chicks (n = 31), raised under standardized conditions, with nine different cognitive tasks. Among these tasks were two replicated novel variants of colour learning and colour reversal problems, tests of positional learning and memory, as well as two different tasks that captured multiple putative measures of inhibitory control and motor-related performance. These task variants were also used to compare subjects' performance on alternative test batteries comprised of different task combinations. Subjects' performance improved with experience, yet we found relatively little consistency in their performance, both within similar tasks using different paradigms and across different tasks. Parallel analysis revealed non-significant factors when all nine tasks were included in a principal axis factor analysis. However, when different combinations of six of the nine tasks were included in principal axis factoring, 14 of 84 combinations revealed significant main factors, explaining between 28 and 35% of the variance in task performance. While comparable findings have been suggested to reflect domain-general intelligence in other species, we found no evidence to suggest that a single factor encompassed a diverse range of cognitive abilities in pheasants. Instead, we reveal how single factor explanations of cognitive processes can be influenced by test battery composition and intra-individual variation in performance across tasks. Our findings highlight the importance of conducting multiple tests within specific domains to ensure robust cognitive measures are obtained.

Reasoning about "Capability": Wild Robins Respond to Limb Visibility in Humans

Little comparative work has focused on what nonhumans understand about what physical acts others are capable of performing, and none has yet done so in the wild, or within a competitive framework. This study shows that North Island robins visually attend to human limbs in the context of determining who to steal food from. We presented 24 wild North Island Robins (Petroica longipes) with two experimenters. Robins could choose to steal a mealworm from one of two experimenters: one whose limbs were exposed and one who underwent a range of visual obstructions in two experiments. In most conditions, robins preferred to steal food located near the experimenter whose limbs were obscured by a cloth or board rather than food located near the experimenter whose limbs were not obscured. The robins’ responses indicate that human limb visibility is associated with reduced access to food. Current findings lay the groundwork for a closer look at the potential general use of causal reasoning in an inter-specific context of using limbs to perform physical acts, specifically within the context of pilfering. This study presents one of the first tests of the role of visual attendance of potential limb availability in a competitive context, and could provide an alternative hypothesis for how other species have passed tests designed to examine what individuals understand about the physical acts others are capable of performing.

Addition and subtraction in wild New Zealand robins

This experiment aimed to investigate proto-arithmetic ability in a wild population of New Zealand robins. We investigated numerical competence from the context of computation: behavioural responses to arithmetic operations over small numbers of prey objects (mealworms). Robins' behavioural responses (such as search time) to the simple addition and subtraction problems presented in a Violation of Expectancy (VoE) paradigm were measured. Either a congruent (expected) or incongruent (unexpected) quantity of food items were hidden in a trap door out of view of the subject. Within view of the subject, a quantity of items were added into (and in some cases subtracted from) the apparatus which was either the same as that hidden, or different. Robins were then allowed them to find a quantity that either preserved or violated addition and subtraction outcomes. Robins searched around the apparatus longer when presented with an incongruent scenario violating arithmetic rules, demonstrating potential proto-arithmetic awareness of changes in prey quantity. This article is part of a Special Issue entitled: Cognition in the wild.

Wild robins (Petroica longipes) respond to human gaze

Gaze following and awareness of attentional cues are hallmarks of human and non-human social intelligence. Here, we show that the North Island robin (Petroica longipes), a food-hoarding songbird endemic to New Zealand, responds to human eyes. Robins were presented with six different conditions, in which two human experimenters altered the orientation or visibility of their body, head or eyes in relation to mealworm prey. One experimenter had visual access to the prey, and the second experimenter did not. Robins were then given the opportunity to 'steal' one of two mealworms presented by each experimenter. Robins responded by preferentially choosing the mealworm in front of the experimenter who could not see, in all conditions but one. Robins failed to discriminate between experimenters who were facing the mealworm and those who had their head turned 90° to the side. This may suggest that robins do not make decisions using the same eye visibility cues that primates and corvids evince, whether for ecological, experiential or evolutionary reasons.

The ability of North Island Robins to discriminate between humans is related to their behavioural type

Animals are able to learn to identify persistent threats to themselves and their offspring. For example, birds are able to quickly learn to discriminate between humans that have previously threatened their nests from humans with whom they have had no prior experience. However, no study has yet examined whether a bird's ability to discriminate between humans is related to the bird's underlying behavioural type. In this study, we examined whether there were differences among North Island (NI) robins (Petroica longipes), based on their underlying behavioural type, in their abilities to discriminate between familiar and novel human observers. Using a simple feeding experiment, we timed how long it took birds to attack a food item placed next to an observer on each of 7 days. On the eighth day, a different observer timed the birds. We found that birds could be split into two behaviour types based on their attack behaviour: fast attackers (latencies <20 sec) and slow attackers (latencies >20 secs). Interestingly, the fast birds did not increase their attack latency in response to the novel observer whereas the slow attackers did. This result, for the first time, demonstrates that a bird's ability to discriminate between humans can vary among birds based on their behavioural type.

Cache sites preferred by small rodents facilitate cache survival in a subtropical primary forest, central China

Context Scatter-hoarding rodents tend to hoard plant seeds in preferred places that facilitate seed survival, resulting in high food rewards for hoarders and a high probability of seedling establishment for plants. Aims To test the hypothesis that caches placed in rodent-preferred microhabitats, nearest-neighbour distances between caches (cache density) or cache depths have an increased chance of survival. Methods Rodent-made caches and observer-established caches of Himalayan hazelnut (Corylus ferox) seeds were tracked in a subtropical primary forest in central China. The survival of caches within rodent-preferred microhabitats, nearest-neighbour distances and cache depths were identified. Key results Rodents preferred to hoard Himalayan hazelnut seeds in microhabitats under and at the edge of shrubs, with the nearest-neighbour distance of <4.0 m, and at 2.1–4.0-cm depth. The survival times of both rodent-made caches and observer-established caches were longer within rodent-preferred microhabitats than in other habitats and increased with an increasing nearest-neighbour distance and cache depth, up to what appeared to be an optimal nearest-neighbour distance and depth. Conclusions Conditions of rodent-preferred cache microhabitats, nearest-neighbour distances and cache depths can facilitate cache survival. Implications Rodents often move plant seeds away from parent trees and bury them in shallow soil, which benefits seed dispersal and establishment of plants. The present study demonstrates that rodent-preferred cache conditions may translate into higher seed survival and a higher tendency of seeds to germinate and establish. Thus, careful management and conservation of rodent-preferred hoarding habitats may benefit seed dispersal and survival.

Adaptive numerical competency in a food-hoarding songbird

Most animals can distinguish between small quantities (less than four) innately. Many animals can also distinguish between larger quantities after extensive training. However, the adaptive significance of numerical discriminations in wild animals is almost completely unknown. We conducted a series of experiments to test whether a food-hoarding songbird, the New Zealand robin Petroica australis, uses numerical judgements when retrieving and pilfering cached food. Different numbers of mealworms were presented sequentially to wild birds in a pair of artificial cache sites, which were then obscured from view. Robins frequently chose the site containing more prey, and the accuracy of their number discriminations declined linearly with the total number of prey concealed, rising above-chance expectations in trials containing up to 12 prey items. A series of complementary experiments showed that these results could not be explained by time, volume, orientation, order or sensory confounds. Lastly, a violation of expectancy experiment, in which birds were allowed to retrieve a fraction of the prey they were originally offered, showed that birds searched for longer when they expected to retrieve more prey. Overall results indicate that New Zealand robins use a sophisticated numerical sense to retrieve and pilfer stored food, thus providing a critical link in understanding the evolution of numerical competency.