Graded Mirror Self-Recognition by Clark’s Nutcrackers

Abstract

The traditional ‘mark test’ has shown some large-brained species are capable of mirror self-recognition. During this test a mark is inconspicuously placed on an animal’s body where it can only be seen with the aid of a mirror. If the animal increases the number of actions directed to the mark region when presented with a mirror, the animal is presumed to have recognized the mirror image as its reflection. However, the pass/fail nature of the mark test presupposes self-recognition exists in entirety or not at all. We developed a novel mirror-recognition task, to supplement the mark test, which revealed gradation in the self-recognition of Clark’s nutcrackers, a large-brained corvid. To do so, nutcrackers cached food alone, observed by another nutcracker, or with a regular or blurry mirror. The nutcrackers suppressed caching with a regular mirror, a behavioural response to prevent cache theft by conspecifics, but did not suppress caching with a blurry mirror. Likewise, during the mark test, most nutcrackers made more self-directed actions to the mark with a blurry mirror than a regular mirror. Both results suggest self-recognition was more readily achieved with the blurry mirror and that self-recognition may be more broadly present among animals than currently thought.

Clark’s Nutcrackers (Nucifraga columbiana) Flexibly Adapt Caching Behavior to a Cooperative Context

“…Though this finding may reflect the birds’ baseline motivational drive to cache (Clayton and Dickinson, 1999), it is in contrast to previous findings that nutcrackers suppress their caching over time in response to witnessing cache theft in a competitive context (Clary and Kelly, 2011; in press). Furthermore, the birds tended to cache more when they were the first bird of the pair to cache, suggesting the birds may have attempted to prevent defection from the partner by appearing more cooperative (though reduced caching was still observed when a bird was the second of a pair to cache).…”

“…Unfortunately, field studies on this aspect of caching behaviors by Clark’s nutcrackers are lacking, with no reports examining differences in caching or pilfering rates between males and females. We have not detected any sex differences for caching rates in competitive experimental contexts (Clary and Kelly, 2011; in press), nor has there been any observations to indicate that nutcrackers may tolerate pilferage of their caches by mates, as has been reported for pinyon jays (Balda, 2002). Clark’s nutcrackers do exhibit extensive bi-parental care, with both the males and females incubating eggs and provisioning hatched young (Tomback, 1998), which would undermine explanations based on parental investment.…”

“…Additionally, the ‘predictors of caching behavior’ analyses revealed that caching decisions were not largely driven by the caches received (reinforcement based), but instead influenced mostly by the activity level of the partner. Similarly, previous research using greater trial numbers has found no positive feedback due to cache recovery (Thom and Clayton, 2014; Clary and Kelly, in press), despite corvids typically learning rapidly in caching tasks (trials 1-3: e.g., Correia et al, 2007; Raby et al, 2007; Clary and Kelly, 2011). Furthermore, when caching behavior has been explicitly tested with respect to associative learning, nutcrackers did not alter their caching behavior when cache loss was paired with an inanimate object (Clary and Kelly, 2011).…”

“…Unlike more social species, nutcrackers only form small, temporary flocks, aggressively defend their territories, and prefer to eat and cache away from others (Tomback, 1998). When examined in a competitive context, nutcrackers suppress caching when observed by a conspecific (Tomback, 1998; Clary and Kelly, 2011; in press), whereas relatively more social Western scrub-jays have been found to increase caching (Emery et al, 2004). During these competitive experiments, birds were allowed to cache either alone or observed by a conspecific.…”

The face of animal cognition

“…Crows and ravens also appear to dislike inequity (Wascher & Bugnyar 2013), while ravens and western scrub jays, Aphelocoma californica, can differentiate between knowledgeable and ignorant conspecifics when those conspecifics do or do not know where food has been hidden (Bugnyar & Heinrich 2005;Clayton et al 2007). Clark's nutcrackers, Nucifraga columbiana, exhibit some form of self-recognition using a mirror (Clary & Kelly 2016), and it is now plausible to suggest corvids as a useful model for human cognitive neuroscience (Clayton & Emery 2015).…”