Cannibalism in Raptors: A Review

Abstract

Feeding strategies, including cannibalism (in which an individual eats a member of the same species), are an important aspect of predator ecology. Cannibalism comprises five forms in raptors: siblicide, filicide, non-parental infanticide, conspecific strife, and conspecific scavenging. Cannibalism by raptors has been documented opportunistically for over a century, but it is unknown how frequent or widespread the behavior is. We performed the first systematic literature review and meta-analyses of the studies documenting filicide, non-parental infanticide, conspecific strife, and conspecific scavenging by raptors. We found 29 reports of these types of cannibalism; we did not review reports of siblicide due to the high frequency of the behavior, making it nearly ubiquitous among raptors. Filicide had nearly twice as many reports (n = 11, 37.9%) as any other type of cannibalism. Most reports were direct observations (n = 23, 79.3%), and nearly half the reports came from North America (n = 14, 48.3%) and approximately a third from Europe (n = 10, 34.5%). The 29 reports involved 25 raptor species from four families, with those from Accipitridae most common (n = 19, 65.5%). Cannibalism in raptors varies but most involves nestlings, which are easier to kill than adults, possibly because brood reduction can help the stronger young survive. Documented reports of cannibalism are increasing, possibly due to recent technological advancements that have increased our ability to document cannibalism and other ecological processes. Nevertheless, we encourage future reports of cannibalism from under-represented locations and for taxa that are less well studied.