Reeve et al (1999) hedgehog mortality factors from rescue centres

Title: Mortality factors affecting wild hedgehogs: A study of records from wildlife rescue centres: A review of original paper by Reeve, N.J. & Huijser, M.P (1999) in Lutra 42; 7-24. 2008

Authors: T. Amory, BWRC Steering Committee

Country: UK & Netherlands

Background to study

A bench study investigating the factors which cause death in hedgehogs based on records, spanning a six-year period, from three wildlife rescue centres and via records provided by the British Wildlife Rehabilitation Council (BWRC) Casualty Recording Scheme. 

Method

• A total of 856 records, detailing the causes of hedgehog mortality between 1992 and 1998 were obtained from two UK and one Dutch wildlife rescue centres.
• A further 11,541 records of hedgehog casualties from 20-30 rescue centres across the UK, from the same time period, were also obtained and included 35% of animals that survived.
• Causes of illness, injury or mortality were categorised by; natural causes; road traffic accidents (RTA’s); injuries from man-made causes (exept RTA’s); orphaned dependent young ; drowned; domestic pet injuries; poisoned or polluted and other.
• Records were analysed against these categories and where available were further quantified by sex, age, number surviving 48 hours, number released, month or quarter of admission and presence of endoparasitie infestations.

Key results

• Hedgehogs accounted for 54% of all mammal casualties admitted to contributing centres (BWRC data).
  • Nearly three quarters of admissions occurred between July and December.
  • Males were more commonly admitted than females but the proportion of males decreased through the year.
• All records revealed that immature individuals (juvenile and subadult) were more frequently admitted (approximately two thirds) than adults (one third).
• Adults and sub-adults were most commonly admitted to centres during the first six months of the year, whilst juvenile admissions rose from 5% (April to June) to 33% and 40% from July to September and October to December respectively.
• 59% of deaths recorded from the three wildlife centres were from natural causes and these were more common during the second half of the year. This was higher than that observed in the BWRC data (28%).
• Mortality in subadults admitted to the three centres due to natural causes was more common than juveniles which were least susceptible.
• Human activity accounted for 41% of deaths recorded from the three wildlife centres.
• Unnatural injuries and RTA’s were most likely from July to September.
• Orphaned individuals were admitted from July onwards.
• Adult males were most likely to die from unnatural injuries and RTA’s.
• Mortality occurred within two days for half of the admitted individuals and 25% survived beyond ten days.
• Endoparasite infestation was common in individuals, of both sexes, that died (64%) but was most common in sub-adults (85%), followed by adults (67%) and dependent young (49%).
• 87% of 315 animals from one centre tested positive for ectoparasites and 7.5% of 664 animals across the three centres had maggots or fly eggs.     

Key messages to landowners and managers derived from these results

• A standardised recording system across wildlife centres which details hedgehog admissions, mortalities, demographics and causes would help to improve knowledge on the main threats to hedgehogs.
• Mortality from road crossings present a large threat, particularly to wider ranging males, thus research and/or accounts of the use of road crossing features such as tunnels or bridges would be beneficial for future conservation strategies.
• Parasite infestation is common in hedgehogs and thus preventative measures to avoid intra and inter species contamination whilst in captive environments is recommended.