Decision time modulates social foraging success in wild common ravens, Corvus corax

Abstract

Social foraging provides several benefits for individuals but also bears the potential costs of higher competition. In some species, such competition arises through kleptoparasitism, that is when an animal takes food which was caught or collected by a member of its social group. Except in the context of caching, few studies have investigated how individuals avoid kleptoparasitism, which could be based on physical strength/dominance but also cognitive skills. Here, we investigated the foraging success of wild common ravens, Corvus corax, experiencing high levels of kleptoparasitism from conspecifics when snatching food from the daily feedings of captive wild boars in a game park in the Austrian Alps. Success in keeping the food depended mainly on the individuals’ age class and was positively correlated with the time to make a decision in whether to fly off with food or consume it on site. While the effect of age class suggests that dominant and/or experienced individuals are better in avoiding kleptoparasitism, the effect of decision time indicates that individuals benefit from applying cognition to such decision‐making, independently of age class. We discuss our findings in the context of the ecological and social intelligence hypotheses referring to the development of cognitive abilities. We conclude that investigating which factors underline kleptoparasitism avoidance is a promising scenario to test specific predictions derived from these hypotheses.

The spatial and temporal exploitation of anthropogenic food sources by common ravens (Corvus corax) in the Alps

“…This finding substantiates existing evidence on the importance of AFSs for non-breeders in this population [23]. We found no difference in movement or foraging behaviour between males and females, supporting previous studies on ravens' space use [23,42,47] and foraging proficiency [72].…”

“…Juveniles and captive-released birds (who were released as juveniles) might lack familiarity with feeding Table 2 Model averaging outputs for the top models based on ∆AICc < = 6 for (a) the occurrence distribution (log-normal distribution) and (b) average maximum daily displacement (log-normal distribution) for 81 individual ravens GPS-tagged for 2.75 years in the Austrian Alps Reference categories: ϮAge class: 'adult' , + origin: 'captive-released' , ‡season: 'autumn' , *year: '2017' , and ǂsex: 'female' . Predictors with a relative variable importance (RVI) greater that 80% (i.e., 0.8) are highlighted in bold along with the respective confidence intervals (95% CI) conditions [72], knowledge of surrounding AFSs, and flying efficiency [73,74], therefore opting for a "local" or less exploratory foraging strategy [71]. In doing so, these individuals could benefit from developing familiarity with their social and spatial environment [14,41,75,76], increasing their experience and establishing social relationships before investing more in exploratory behavior [15,33,77].…”

“…Furthermore, at communal AFSs, subordinate birds benefit from having power in numbers to overcome defenses at food resources [78], however this is not necessarily the case in other soaring scavengers [79,80]. In contrast, adults and wild-caught birds that are more experienced with the landscape could mitigate high levels of competition by searching for and exploiting non-communal AFSs [33,49,72]. With age, exploration may also increase as individuals search for partners and territories [81,82].…”

Who is crying wolf? Seasonal effect on antipredator response to age-specific alarm calls in common ravens, Corvus corax

“…Although ravens face severe foraging competition in winter (Heinrich, 1989) and may divide their attention between gaining access to food (B. Heinrich & Marzluff, 1995), fending off conspecific kleptoparasitism and cache pilferage (Bugnyar & Kotrschal, 2002;Gallego-Abenza, Loretto, & Bugnyar, 2020;Heinrich & Pepper, 1998), there are hardly any indications that competition for food affects their antipredator behaviour, at least not at our study site (Nácarová et al, 2018). Finally, the temporal pattern found might be considered an artefact of our testing.…”