Data from: Kelp and dolphin gulls cause perineal wounds in South American fur seal pups (Arctocephalus australis) at Guafo Island, Chilean Patagonia

During five reproductive seasons, we documented the presence, extent and origin of perineal wounds in South American fur seal pups (Arctocephalus australis) on Guafo Island, Northern Chilean Patagonia. The seasonal prevalence of perineal wounds ranged from 5 to 9%, and new cases were more common at the end of the breeding season (February), when pups were on average two months old and were actively expelling hookworms (Uncinaria sp). Histologically, wounds corresponded to marked ulcerative lymphoplasmacytic and histiocytic dermatitis with granulation tissue and mixed bacterial colonies. In 2015 and 2017, kelp gulls (Larus dominicanus) and dolphin gulls (Leucophaeus scoresbii) were observed picking and wounding the perineal area of marked pups. This behaviour occurred more frequently after the pups' defecation, when sea gulls engaged in consumption of pups' faeces. The affected pups usually had moderate to marked hookworm infections along with bloody diarrhoea and anaemia. Pups with severe wounds (23% of affected animals) had swollen perineal areas and signs of secondary systemic bacterial infection. We propose that seagulls on Guafo Island have learned to consume remains of blood and parasites in the faeces of pups affected by hookworm infection, causing perineal wounds during this process. We conclude that this perineal wounding is an unintentional, occasional negative effect of an otherwise commensal gull–fur seal relationship.在五个繁殖季期间，我们于智利巴塔哥尼亚北部瓜福岛（Guafo Island）记录了南美毛皮海狮（Arctocephalus australis）幼崽会阴部伤口（perineal wounds）的发生情况、损伤范围及致病成因。该类会阴部伤口的季节流行率介于5%至9%之间，新增病例多集中于繁殖季末期（2月）；此时幼崽平均月龄为2个月，正处于主动排出钩虫（Uncinaria sp）的阶段。组织病理学检查显示，此类伤口表现为伴有肉芽组织形成与混合菌菌落定植的重度溃疡性淋巴浆细胞性及组织细胞性皮炎。2015年与2017年，研究人员观察到海带鸥（Larus dominicanus）和海豚鸥（Leucophaeus scoresbii）啄咬并损伤了标记幼崽的会阴部区域。该行为多发生于幼崽排便后，此时鸥类会取食幼崽的粪便。受影响的幼崽通常伴有中至重度钩虫感染，同时出现血性腹泻与贫血症状。伤口严重的幼崽（占受影响个体的23%）会出现会阴部肿胀及继发性全身细菌感染的征象。我们推测，瓜福岛的鸥类已形成取食受钩虫感染幼崽粪便中血液与寄生虫残留物的行为，该过程会导致幼崽出现会阴部伤口。综上，我们认为此类会阴部损伤是鸥类与南美毛皮海狮之间原本共栖关系中，一种偶然发生的非故意负面效应。