An investigation of non-spatial cognitive abilities in an asocial corvid, the Clark\u27s nutcracker (Nucifraga columbiana)

A great deal of research suggests that the cognitive abilities of birds in the family Corvidae (crows and jays) are comparable in many aspects to that of apes. Scientists have posited competing hypotheses to explain how complex cognitive abilities arise in a species or group of animals. One such hypothesis, the social-intelligence hypothesis, states that the demands of living in a large, dynamic group drive an animal\u27s need for complex cognitive skills. The ecological-intelligence hypothesis, predicts that generalist foragers develop more highly flexible behaviors and a wider cognitive repertoire than specialist foragers. To date, cognitive research on corvids has focused on corvids that are highly social and are generalist foragers. From a comparative standpoint, I examined the cognitive abilities of a corvid that is relatively asocial and a specialist forager. The Clarks\u27 nutcracker (Nucifraga columbiana) is thought to be perhaps the least social corvid, and it largely specializes on the seeds of one species of pine (Pinus edulis). I tested nutcrackers using several tasks in three broad areas of cognition: inferential reasoning, numerical discrimination, and social intelligence. These experiments represent novel tests of cognitive abilities in this species. I found that the nutcrackers performed in a similar manner as social mammals and corvid birds, in all three areas of cognition. This suggests that social group size may not have a large impact on the development of a broad range of problem solving skills. Rather, ecological pressures associated with finding, extracting, caching and protecting seeds from pilferage may have influenced the development of complex cognition in this species

Factors affecting aggression during nest guarding in the Eastern red-backed salamander (Plethodon cinereus)

Defending young against intruders is a potentially risky behavior, and is energetically costly. Yet female eastern red-backed salamanders, Plethodon cinereus, guard their clutches for many weeks and aggressively defend eggs against predators and conspecifics. I examined the effect of clutch age, clutch size, and attendant size on the level of aggression attained during nest defense by staging conspecific invasions of nests of brooding female P. cinereus in the laboratory. I predicted that older and larger clutches would elicit increased aggression from the guarding females, and that larger females would be more aggressive when defending. The females were significantly more aggressive when guarding older clutches (6 wk postoviposition) than younger clutches (4 wk postoviposition). However, there was no difference in aggressive behavior when females guarded large (10-egg) or small (4-egg) clutches. There was also no relationship between body size and level of aggression; females were aggressive regardless of their size. These results suggest that females are able to evaluate the age (or developmental stage) of their eggs and adjust expenditure accordingly, but are not differentially responsive to clutch size

Tests of inferential reasoning by exclusion in Clark’s nutcrackers (Nucifraga columbiana)

We examined inferential reasoning by exclusion in the Clark’s nutcracker (Nucifraga columbiana) using two-way object-choice procedures. While other social scatter-hoarding corvids appear capable of engaging in inferential reasoning, it remains unclear if the relatively less social nutcracker is able to do so. In an initial experiment, food was hidden in one of two opaque containers. All of the birds immediately selected the baited container when shown only the empty container during testing. We subsequently examined the nutcrackers in two follow-up experiments using a task that may have been less likely to be solved by associative processes. The birds were trained that two distinctive objects were always found hidden in opaque containers that were always positioned at the same two locations. During testing, one of the two objects was found in a transparent “trash bin” and was unavailable. The birds were required to infer that if one of the objects was in the “trash,” then the other object should still be available in its hidden location. Five out of six birds were unable to make this inference, suggesting that associative mechanisms likely accounted for our earlier results. However, one bird consistently chose the object that was not seen in the “trash,” demonstrating that nutcrackers may have the ability to use inferential reasoning by exclusion to solve inference tasks. The role of scatter hoarding and social organization is discussed as factors in the ability of corvid birds to reason

Numerical cognition in the Clark’s nutcracker, Nucifraga columbiana.

Abstract We examined quantity discrimination in the Clark’s nutcracker (Nucifraga columbiana), a corvid bird with a strong dependence upon caching and recovering nuts. We presented 2 sets of nuts simultaneously, in 21 different conditions, to see if the nutcrackers could choose the larger of the 2 quantities. The nutcrackers displayed a strong ability to discriminate quantities of nuts. Like other animals tested previously, the nutcrackers’ performance decreased as the ratio of the 2 quantities approached 1. Interestingly, at constant distances, the nutcrackers did not have more difficulty with contrasts containing larger quantities. Thus, nutcrackers have a fine sensitivity for discriminating between 2 quantities. We review the relevant literature and explore the possibility that nutcrackers, like some other birds, may have developed a keen ability to discriminate quantities. This ability may have developed as an adaptive specialization to cope with their scatter-hoarding ecology, though the evidence for such a conclusion is mixed

Clark’s nutcrackers (Nucifraga columbiana) are sensitive to distance, but not lighting when caching in the presence of a conspecific

We examined the caching behavior of the Clark’s nutcracker (Nucifraga columbiana), a relatively asocial corvid bird, during social and non-social conditions with conspecifics. Past work by Dally et al., 2004 ; Dally et al., 2005a has found that the related but more social scrub jay (Aphelocoma californica) caches food in locations that are far away or that are more dimly illuminated when in the presence of an observer. Here, we used procedures comparable to those of Dally’s group to examine if the less social nutcracker is also sensitive to these same factors when caching in the presence of a conspecific. We found that nutcrackers cached nuts farther away, but showed no preference for caching in a dimly compared to a brightly illuminated area when in the presence of a conspecific observer. When comparing the measures of cache protection used in the past work with scrub jays the results are consistent with the social organization of these birds; that is, the less social nutcracker engaged in fewer cache protection behaviors than the more social scrub jays, However, we explore other possible explanations for our findings given the wider body of literature on corvid cache protection suggesting that nutcrackers and scrub jays may be more comparable

Clark’s nutcrackers (Nucifraga columbiana) use gestures to identify the location of hidden food

Heterospecific cues, such as gaze direction and body position, may be an important source of information that an animal can use to infer the location of resources like food. The use of heterospecific cues has been largely investigated using primates, dogs, and other mammals; less is known about whether birds can also use heterospecific gestures. We tested six Clark’s nutcrackers in a two-way object-choice task using touch, point, and gaze cues to investigate whether these birds can use human gestures to find food. Most of the birds were able to use a touch gesture during the first trial of testing and were able to learn to use point and gaze (eyes and head alternation) cues after a limited number of trials. This study is the first to test a non-social corvid on the object-choice task. The performance of non-social nutcrackers is similar to that of more social and related corvids, suggesting that species with different evolutionary histories can utilize gestural informatio