Data from: Group foraging increases foraging efficiency in a piscivorous diver, the African penguin

Marine piscivores have evolved a variety of morphological and behavioural adaptations, including group foraging, to optimize foraging efficiency when targeting shoaling fish. For penguins that are known to associate at sea and feed on these prey resources, there is nonetheless a lack of empirical evidence to support improved foraging efficiency when foraging with conspecifics. We examined the hunting strategies and foraging performance of breeding African penguins equipped with animal-borne video recorders. Individuals pursued both solitary as well as schooling pelagic fish, and demonstrated independent as well as group foraging behaviour. The most profitable foraging involved herding of fish schools upwards during the ascent phase of a dive where most catches constituted depolarized fish. Catch-per-unit-effort was significantly improved when targeting fish schools as opposed to single fish, especially when foraging in groups. In contrast to more generalist penguin species, African penguins appear to have evolved specialist hunting strategies closely linked to their primary reliance on schooling pelagic fish. The specialist nature of the observed hunting strategies further limits the survival potential of this species if Allee effects reduce group size-related foraging efficiency. This is likely to be exacerbated by diminishing fish stocks due to resource competition and environmental change.

海洋食鱼动物（marine piscivores）已演化出多种形态与行为适应策略，包括群体觅食行为，以在捕食集群鱼类（shoaling fish）时提升觅食效率。尽管已知企鹅会在海洋中聚集并以这类猎物为食，但目前仍缺乏实证证据表明，与同种个体（conspecifics）一同觅食可提升其觅食效率。本研究对佩戴动物搭载式视频记录仪（animal-borne video recorders）的繁殖期非洲企鹅的捕猎策略与觅食表现进行了考察。这些企鹅既会捕食单独活动的鱼类，也会捕食集群远洋鱼类（schooling pelagic fish），同时展现出单独觅食与群体觅食两种行为模式。效率最高的觅食行为发生在潜水上升阶段，此时企鹅会将鱼群向上驱赶，多数捕获的为去极化鱼类（depolarized fish）。相较于捕食单独鱼类，以集群鱼类为食时的单位努力渔获量（Catch-per-unit-effort）显著提升，群体觅食时这一优势更为明显。与广食性企鹅物种不同，非洲企鹅似乎已演化出专门化的捕猎策略，这与其主要依赖集群远洋鱼类的食性高度相关。若阿利效应（Allee effects）削弱了群体规模相关的觅食效率，那么观测到的专门化捕猎策略特性将进一步限制该物种的生存潜力。而资源竞争与环境变化导致的鱼类种群衰减，可能会进一步加剧这一危机。