Oscillatory extraction behaviour suggests functional attributes of crows’ hooked-stick tools

Abstract

New Caledonian crows are the only nonhuman animals known to craft hooked-sticks for use in foraging. Since their first description over 25 years ago, researchers have been unable to provide a detailed account of how these complex tools function in natural probe sites. Using close-up video footage, we document how a New Caledonian crow operated a hooked-stick to extract a large tree weta from a chamber in a tree trunk. The extraction technique had two distinct, separate components: (1) simultaneous oscillating head rotation and reciprocating bill action, and (2) measured pulling with the tool. Analysis of this first detailed field observation of hooked-stick use suggests a link between hooked-stick tool characteristics, functionality and skilled manipulation in natural prey extraction by these technological birds. Our findings also provide a rare, if not novel, example of tool-associated oscillatory manipulation in nonhuman animals.

When the owner does not know: comparing puppies and adult dogs’ showing behavior

Abstract

Domestic dogs have been shown to engage in interspecific communication with their owners using a flexible repertoire of signals (i.e., gaze, vocalizations, and postures). This ability is influenced by ontogenetic development as well as breed selection. Different aspects of this phenomenon have been studied using the out of reach/hidden object task in which a piece of food is shown to the dog and then hidden in an unreachable spot by the experimenter. Dogs’ behavioral displays toward the target and the owner (ignorant about the location of the food) have been observed. The complex communicative behavior dogs exhibit in this context is defined as showing behavior and includes attention-getting components directed toward the owner, and directional components directed toward the target. No study has investigated the ontogenetic development of this behavior. In the current study, we compared the showing behavior in 4–6 month old puppies and 2–11 year old adults in an out of reach task involving the hiding of a food reward in one of two cabinets. Dogs were exposed to three conditions: (1) Owner with Food (OF), (2) Owner No Food (ONF), and (3) Alone with food (AF). Dogs showed more gaze alternations when both the food and the owner were present confirming the intentional and referential nature of this behavior. Contrary to our expectations, we found no differences between the showing behaviors of 4–6 month old puppies and adult dogs. This study provides interesting preliminary evidence of showing behavior in puppies. Further studies are needed to gain a deeper understanding of the factors influencing this communicative behavior (i.e., breed, level of training). Furthermore, longitudinal studies should be performed from the age of 2 months up to 1 and 2 years to better clarify the influence of development and experience on showing behavior in domestic dogs.