A review of northern bottlenose whale (Hyperoodon ampullatus) strandings in the UK, 1990-2008

Abstract

Northern bottlenose whales (NBW) (Hyperoodon ampullatus), are a deep water, pelagic species, usually found beyond continental shelve edges. Between 1990 and 2008, the UK Cetacean Strandings Investigation Programme received reports of 28 NBW strandings in the UK, including the now famous „Thames whale“ in 2006. Although the majority of strandings took place on the west and north-west coast of the UK, recent strandings have occurred more frequently on the east coast of the UK. The majority of strandings occurred between July and November and generally involved juvenile or sub-adult animals with no apparent sex bias. Ten individuals were subjected to a full necropsy. The causes of death were live stranding (n=7) and infectious disease (fungal encephalitis, n=1). A cause of death was not established in two cases. The stomach contents were examined during necropsy. Recently ingested prey was absent in all cases, but squid beaks were found in several of the animals and subsequently identified as Gonatus fabricii. It is not known how long these may persist within the animals digestive system to give an accurate indication of how long the animals had not been able to feed. Three animals that stranded alive had blood samples taken pre-mortem. Results showed severe dehydration, renal failure and muscle damage in all three cases. Dehydration may result from an inability to feed and uptake water from prey. Pathological evidence of skeletal and myocardial rhabdomyolysis and myoglobinuria was evident in these cases and is likely to be exacerbated by crushing under the animal’s own body weight once the animals had stranded alive. The reason/s for these NBWs finding their way into the shallow coastal waters of the UK are still not known, but potential causes include anthropogenic noise from a variety of sources (including mid-frequency [...].