Hartpury Student Research Journal

Home » Issue 3 (Summer 2017) » Project Articles » Factors affecting the admittance and survival rates of European Hedgehogs (Erinaceus europaeus) within two rehabilitation centres

Factors affecting the admittance and survival rates of European Hedgehogs (Erinaceus europaeus) within two rehabilitation centres

Author Names: Alice Woodward (BSc (Hons) Bioveterinary Science) and Lucy Bearman-Brown

 

Abstract:

Habitat degradation and fragmentation is causing a decrease in global biodiversity. This affects a wide range of species, including the West European Hedgehog (Erinaceus europaeus). In 2015, the West European Hedgehog population was estimated at a declining 1 million, so increased conservation efforts have been established to minimise the reduction. Whilst national surveys have been undertaken, the true extent of the decline has yet to be quantified. Wildlife hospitals and rehabilitation centres are often on the frontline for wildlife causalities and diseases and so are an adequate source of information when identifying illness within populations. However, there is little information on the population numbers within centres and the effect these centres have on the survival of hedgehogs.

The aim of this study was to assess the factors affecting admittance and survival rates of hedgehogs within two rehabilitation centres. The study collated data from two rehabilitation centres over a 16-month period and assessed factors potentially  affecting the cause of admission, and the overall survival outcome of the animals.

Sample size differed between both centres. Both were found to release greater numbers of animals than died, and significantly larger numbers of males were admitted than females at both centres. Breeding season and hibernation were found to affect the number of admittances. Outcome was shown to be affected by the duration of stay, but not by gender, with most animals dying within the first 5 – 10 days of admittance. This study did not take into account the injuries received by the animals though, and the reason for admittance, which could have been useful in interpreting the results. Through this study, information on current populations within rehabilitation centres and a greater understanding of the effect of rehabilitation on survival rate has been obtained.

 

1.0 Introduction

Increased pesticide use and habitat fragmentation and degradation are leading to a reduction in global biodiversity. The West European hedgehog (Erinaceus europaeus) provides an example of this (People’s Trust for Endangered Species (PTES), 2015). The West European hedgehog is a nocturnal insectivore, often observed inhabiting rural and urban environments (Silaghi et al., 2012). Whilst this species is commonly located across Western Europe and other non-native continents, the population within the UK is said to be declining (Hof and Bright, 2010; Jackson, 2006). Historically, hedgerows surrounding arable farmland makes a suitable habitat for hedgehogs, however, land management and pesticide use has caused a reduction in the habitat diversity and invertebrate species available to hedgehogs (Hof and Bright, 2010). Moreover, urbanisation of areas and resultant habitat fragmentation  has led to an increased risk of road mortalities and more impenetrable features producing minimal areas of suitable habitat (Dowding et al., 2010; Baker and Harris, 2007). Hubert et al. (2011) argue though that “urban adapters” such as the hedgehog are actually more abundant in these areas because they can make use of the alternative shelters created by these structures . Furthermore, predation risk by the European Badger (Meles meles) is also greatly reduced within these environments, causing hedgehogs to gravitate towards these suburban areas (Young et al., 2006).

The hedgehog population within Great Britain was estimated to be approximately 30 million in the 1950s (Wembridge, 2011). Since then, further surveys have yielded population figures of 1.55 million in 1995 and roughly 1 million in 2015 (PTES, 2015). Whilst there has never been a national census to confirm the accuracy of these figures (Wembridge, 2011) the continued suggested population decline is causing concern amongst conservationists (Hof and Bright, 2010). In 2012, Roos, Johnston and Noble compiled data from seven regional and national surveys to determine the feasibility of generating hedgehog population trends. Four of the surveys conducted evidenced a significant decline in hedgehog populations within a 4 to 14 year period (Roos, Johnston and Noble, 2012). In contrast, the two other surveys analysed within this study evidenced a slight increase in occupancy rates within areas (Roos, Johnston and Noble, 2012; Royal Society of the Protection of Birds (RSPB), 2010). However, the method used to obtain data within these surveys asked for volunteers to record hedgehog sightings, and therefore could have issues with potential bias; RSPB, 2010). Whilst Delaney et al. (2008) suggest that if the species are easily identifiable then data provided by volunteers should have a high accuracy,  Silvertown (2009) disputes this, and suggests that the data collected will lack the rigour and standardisation of that obtained by professional scientists. This was evident in one of the surveys analysed, as there was an increased response rate where hedgehogs were continually detected (Roos, Johnston and Noble, 2012). Due to the current decline in hedgehogs it is increasingly important that data obtained by volunteers is as accurate and reliable as possible (Williams, Stafford and Goodenough, 2015). In order to minimise the decline, in 2007, the species was added to the UK Biodiversity Action Plan and listed as a priority species (Joint Nature Conservation Committee (JNCC), 2016; Wembridge and Langton, 2016; Department of Environment, Food and Rural Affairs (DEFRA), 2011).

In addition to legislative protocols, it is important to underpin the exact causes of the decline (PTES, 2015; Gaglio et al., 2010). Whilst field surveying is a reliable form of observing population and habitat changes, the data often gives little information on diseases, malnourishment, injury or parasite prevalence (Martinez, Rosique and Royo, 2014; Skuballa, 2009). Whilst parasitic burdens are often reported within hedgehogs admitted to wildlife centres, this does not indicate their prevalence within the wild population (Irvine, 2006; Simpson, 2002). Bunnell (2001) assessed the incidence of disease and injury within hedgehogs admitted to a wildlife centre over a two year period; 27% of all cases admitted were due to malnutrition, whilst 35% had parasites. Additionally, males and nestlings were reported to have a higher admittance rate than females, although the effect such variables have on survival remain speculative within captivity (Molony et al., 2007; Bunnell 2001)

An estimated 800 wildlife rehabilitators and hospitals within the UK are on the frontline for injured and diseased mammal cases, with hedgehogs being among the most commonly admitted (PTES, 2015; Gaglio et al., 2011). Although current populations within these hospitals and rehabilitation centres have not been quantified (Grogan and Kelly, 2013). In order to gain more information upon wildlife populations within rehabilitation centres, Grogan and Kelly (2013) provided a review of RSPCA data. The study analysed admittance to four wildlife hospitals and found that 40% of hedgehogs admitted were released. However, the exact numbers of hedgehogs and time periods within this study are unspecified and so challenging to compare to other studies (Grogan and Kelly, 2013).  Furthermore, the RSPCA are unlikely to release animals if there is no chance the animal can integrate with the wild population (e.g. amputation) and therefore, will not release the animal, even into a secure environment (Grogan and Kelly, 2013). However, there is little research published in relation to the release of hedgehogs following an amputation, so release criteria within this study may not be applicable to all centres (Bullen, 2013). Whilst a number of other organisations have gathered data on hedgehogs within wildlife hospitals and centres, the information that this data may provide into the long-term assessment of hedgehog populations has not been fully investigated (Toms and Newson, 2006)

The survival success rates of hedgehogs released post – rehabilitation have been studied to assess the impact of rehabilitation on hedgehog survival in the wild (Molony et al., 2006; Reeve, 1998). Reeve (1998) concluded that there was an 83% survival rate within the first two weeks of release, although this declined to a 25% survival rate at approximately 16 weeks. In contrast, Molony et al. (2006) found a survival rate of 73% over a period of seven weeks. However, Reeve used a smaller and less representative sample size (n = 12) than Molony et al. (2006), (n = 109), which could have influenced the results. Molony et al. (2006) also conducted the study over a smaller time frame than Reeve (1998) and so the survival rates could have been  lower if the time period had been extended. Reeve (1998) further argued that the release site used within his study may have also increased the risk of road mortalities to the hedgehogs and suggested survival rates would have been greater if an alternative release site had been used. Although the studies varied in their results, both stated that hedgehogs are able to maintain bodyweight and condition upon release (Molony et al., 2006; Reeve 1998). Furthermore, Molony et al. (2006) suggested that further studies are required to establish the optimum duration of stay within wildlife hospitals to achieve successful survival following release.

 

1.1 Aims and Objectives

The main aim of this study will be to assess the factors affecting admittance and survival rates of hedgehogs within two rehabilitation centres. The study will determine whether there are differences between gender and admittance, gender and duration of stay, gender and survival outcome and duration of stay and survival outcome between the rehabilitation centres. In order to achieve these objectives, hedgehog admittance data will be collected from two rehabilitation centres. The data will include information on gender, the date of admittance, the date of release/ death and the outcome of the animal.

The null hypothesis assumes that there will be no significant differences between gender and admittance, and no significant difference between gender and survival outcome. The null hypothesis also assumes that there will no significant difference between duration of stay and survival outcome, and no significant difference between duration of stay and gender. Completion of this analysis should provide more information regarding the potential benefits of wildlife rehabilitation centres, and the effects of rehabilitation on the hedgehog population.

 

2.0 Methodology

In order to obtain retrospective data for this study, wildlife rehabilitors within the UK were contacted. Wildlife centres and hospitals across the country were emailed to request access to their data. The hedgehog admittance data required for this study was; gender, admittance date, release or death date and outcome. This was based on Bunnell (2001), who analysed the admittance data of one rehabilitation centre over a three year period. The study was designed to gain details of the records of hedgehogs admitted within as large a time frame as possible (Molony et al., 2007). All centres used within this study gave permission for their data to be used and to be named within subsequent reports.

Data were received from two centres: Oak and Furrows and Jersey, and this was inputted into a Microsoft Excel® spreadsheet. Duration of stay for the two centres was calculated in days within Microsoft Excel® using the admittance date and outcome date. Percentages and monthly admission figures were calculated through Microsoft Excel® so as to make the data more easily interpretable and comparable to previous studies (Bunnell, 2001).  Data were then transferred from Microsoft Excel into the current version of IBM ® SPSS v.23 ® where further analyses were performed. Any individual records where data was missing were excluded from the analysis. Due to the size of the data set, all complete variables listed were tested for normality using the Shapiro Wilks test (Razali and Wah, 2011). After completing normality tests, further tests for significant differences (Mann Whitney U and Pearson Chi – Squared) were conducted between the variables (gender, duration of stay, and outcome). This was based upon research by Molony et al. (2007) who analysed the data of four rehabilitation centres over a four year period.

A Kaplan-Meier survival analysis was also performed between duration of stay and outcome so as to estimate the probability of survival past given time points (Goel, Khanna and Kishore, 2010; Rich et al., 2010).  A Kruskal-Wallis test was performed alongside this so as to assess differences between the duration of stay and survival outcome across both centres (Elliot and Hynan, 2011). This was based upon analyses performed by Molony et al. (2007).

 

3.0 Results

3.1 Descriptive Statistics

In total 1311 individual records were obtained; 439 from Oak and Furrows and 872 from Jersey. The records obtained were covered a 16-month period. Of the 439 records received from Oak and Furrows, 248 of these records were complete. Of the 872 records obtained from Jersey, 745 were complete.

 

3.2 Gender vs. Admittance

Of the total complete admittances to Oak and Furrows (Figure 1), 144 males were admitted (58%) and 104 females were admitted (42%), (1.42 ± 0.49). Of the total complete admittances to Jersey (Figure 1), 384 males were admitted (52%) and 361 females were admitted (48%), (1.48 ± 0.50).

There was a significant difference between both centres with significantly more male and female hedgehogs being admitted to Jersey than Oak and Furrows (Pearson Chi Square: X22 = 5.065, P = 0.024).

Figure 1

Figure 1. The total number of hedgehogs admitted to both centres, defined by gender.

 

3.2.1 Monthly Admittance

The highest number of males were admitted to Oak and Furrows in November 2015 (n = 18) and July 2016 (n = 18) and the highest number of females were admitted in November 2015 (n = 24), (Figure 2). No females were admitted in March 2016 and no males were admitted in September 2016.

Figure 2

Figure 2. The total number of male and female hedgehogs admitted to Oak and Furrows from September 2015 – December 2016.

The highest number of males were admitted to Jersey in October 2015 (n= 43) and the highest number of females were admitted in November 2015 (n = 48) and July 2016 (n = 48), (Figure 3). The lowest number of female admittances was recorded in February 2016 (n = 1) and the lowest number of male admittances was recorded in March 2016 (n = 4).

Figure 3- Woodward

Figure 3. The total number of male and female hedgehogs admitted to Jersey from September 2015 – December 2016.

 

Overall, the highest number of male hedgehogs were admitted to both centres in October 2015 (n = 56) and the highest number of female hedgehogs were admitted in November 2015 (n = 72), (Figure 4). The lowest number of male hedgehogs were admitted in March 2016 (n = 9) and the lowest number of female hedgehogs were admitted in February 2016 (n = 3) and March 2016 (n = 3).

Figure 4

Figure 4. The total number of male and female hedgehogs admitted to Oak and Furrows and Jersey from September 2015 – December 2016.

 

3.3 Gender vs. Outcome

Of the total number of hedgehogs admitted to Oak and Furrows (n = 248), 79 males were released (32%) and 58 females were released (23%). Of the total complete admittances to Jersey (n = 745), 210 males were released (28%) and 192 females were released (26%).

Of the total complete admittances to Oak and Furrows (n = 248), 65 males died (26%) and 46 females died (18%). Of the total complete admittances to Jersey (n = 745), 174 males died (23%) and 169 females died (23%).

There was no significant difference found between male and female survival outcome at Oak and Furrows (Pearson Chi Square: X22 = 0.020, P = 0.887) or at Jersey (Pearson Chi Square: X22 = 0.169, P = 0.681). Further analysis between both centres showed a significant difference such that significantly more males and females were released and died at Jersey than Oak and Furrows (Figure 5) (Pearson Chi Square X22 = 993. 306, P < 0.001).

Figure 5

Figure 5. The total number of released and dead hedgehogs at each centre, defined by gender.

 

3.4 Gender vs. Duration of Stay

There was no significant difference between the number of males and females admitted to Oak and Furrows and the duration of stay (Mann-Whitney U: U = 7434.5, N1 = 144, N2 = 104, P = 0.923). No significant difference was also found between the number of males and females admitted to Jersey and the duration of stay (Mann-Whitney U: U = 68002.5, N1 = 384, N2 = 361, P = 0.655).

No significant difference was found between the combined number of males and females admitted and the duration of stay between the two centres (Mann-Whitney U: U = 121443.0, N1 = 528, N2 = 465, P = 0.770).

 

3.4.1 Gender vs. Duration of Stay (Monthly)

The greatest duration of stay for males within Oak and Furrows was in January 2016 (105.4 ± 8.65) (Figure 6). The greatest duration of stay for females at Oak and Furrows was recorded in September 2015 (216.5 ± 6.5), however, this is believed to be an outlier from two females. No duration of stay was recorded for males in September 2015 and no duration of stay was recorded for females in March 2016. The next lowest duration of stay, recorded for males, was in December 2016, (8.2 ± 1.45) and the next lowest duration of stay, recorded for females, was in December 2016, (6.5 ± 2.5).

Figure 6

Figure 6. The mean average duration of stay of male and female hedgehogs at Oak and Furrows from September 2015 – December 2016.

 

The greatest duration of stay, recorded for males admitted to Jersey, was in October 2015 (72 ± 8.15) (Figure 7). The greatest duration of stay, recorded for females, was in October 2015 (71.2 ± 8.4). The lowest duration of stay, recorded for males, was in March 2016 (12.6 ± 6.4) and the lowest duration of stay, recorded for females was in February 2016.

Figure 7

Figure 7. The mean average duration of stay of male and female hedgehogs at Jersey from September 2015 – December 2016.

 

Overall, the longest duration of stay, at both centres, recorded for males was in January 2016 (151.3 ± 12.42) and the longest duration of stay recorded for females was in September 2015 (257.76 ± 23.3). The lowest duration of stay recorded for males was in December 2016 (21± 2.54) and the lowest duration of stay recorded for females was in December 2016 (20.2 ± 3.10) (Figure 8).

 

Figure 8

Figure 8. The mean average duration of stay of male and female hedgehogs admitted to both centres from September 2015 – December 2016.

 

3.5 Duration of Stay vs. Outcome

A significant difference between duration of stay and outcome at Oak and Furrows was identified such that significantly more hedgehogs died within the first five to ten days (Mann-Whitney U: U = 14405, N1 = 111, N2 = 137, P < 0.001). There was also a significant difference between duration of stay and outcome at Jersey such that significantly more hedgehogs died within the first five to ten days of admission (Mann-Whitney U: U = 123859, N1 = 343, N2 = 402, P < 0.001)

 

 

Further analysis also showed a significant difference in duration of stay and outcome between both centres (Kruskal-Wallis test: H11 = 508.16, P <0.001). Pairwise comparisons with adjusted P values, showed that significantly more hedgehogs were released at Oak and Furrows than hedgehogs who died at Jersey (P <0.001). Significantly more hedgehogs were also released at Jersey than died at Oak and Furrows (P <0.001). No significant difference was observed between the number of hedgehogs released at Jersey and the number of hedgehogs released at Oak and Furrows (P = 0.906). No significant difference was observed between the number of hedgehogs who died at Jersey and died at Oak and Furrows (P = 1.000).

Kaplan – Meier survival analysis showed the dispersal of released hedgehogs in relation to dead hedgehogs across both centres (Figure 9). No hedgehogs admitted to Oak and Furrows who died survived past 48 days. Any data with a duration of stay over 150 days are considered as outliers. The maximum stay for hedgehogs released from Oak and Furrows ranged from 0 to 223 days. Overall, hedgehogs admitted to Jersey had a duration of stay ranging from 0 to 306 days. Hedgehogs released from Jersey had a duration of stay up to 207 days. 55.2% of all hedgehogs admitted to Oak and Furrows were released and 54% of all hedgehogs admitted to Jersey were released. Overall, 54.3% of hedgehogs admitted were released.

 

Figure 11

Figure 9. Kaplan-Meier analysis of duration of stay and negative outcome, of hedgehogs, at Oak and Furrows and Jersey.

 

Survival estimates conclude that the probability of survival from both centres is lowest on day two of admission, after which survival chances increase (Table 1.). The data also shows that hedgehogs have the greatest chance of survival after 15 days of care within both centres (Table 1.).

Table 1. Kaplan – Meier analysis estimating the probability of survival of hedgehogs admitted to Oak and Furrows and Jersey between 0 to 60 days.

Table 1

 

4.0 Discussion

There are many intrinsic factors that are suggested to affect the overall outcome of an animal surviving within a rehabilitation centre or wildlife hospital (Ashraf and Menon, 2005; Molony et al., 2007). Molony et al. (2007) suggest that the length of time in captivity affects the survival outcome due to the close proximity to humans and the addition of stressful novel stimuli. Via statistical analysis the effect of some of these factors can be assessed to show the effect of rehabilitation on the animals and hopefully provide information that may help ultimately improve the animal’s welfare (Tribe and Brown, 2000). Furthermore, the data provided will be able to inform other organisations of localised populations within centres. In this present study, factors such as; admittance, gender, duration of stay and outcome were assessed.

 

4.1 Gender vs. Admittance

Oak and Furrows and Jersey were both found to have higher levels of male admission than females. This correlates with the male-biased findings of Bunnell (2001). Bunnell (2001) suggested the reason for this finding could be due to a higher proportion of males being born, however, Rondinini and Doncaster (2002), citing Reeve and Huijser (1999), indicate that males are more likely to be admitted to centres due to road traffic casualties. Breeding season and dispersal periods often result in high numbers of road traffic injury and mortality in hedgehogs due to their slow movement and the barriers that roads present (Haigh et al., 2014). Males are more likely to succumb to injury on roads due to the expansion of their territories during breeding season and the earlier awakening after hibernation (Haigh et al., 2014; Rondinini and Doncaster, 2002). This is further evidenced by the monthly admittance data. Between January 2016 and June 2016, more males were admitted to the centres than females. However, injuries and geographical locations of the findings of these animals were not taken into consideration. Consideration of these factors would greatly improve further studies.

Peak admittance of female hedgehogs to Oak and Furrows and Jersey occurred in November 2015 and July 2016. This correlates with the findings of Bunnell (2001) who also observed an increase in the number of juvenile hedgehogs admitted within November. Bunnell (2001) citing Reeve (1994) suggest that this occurs in relation with the breeding season. Females can have up to two litters per year, with the second litter occurring in the autumn (Jackson, 2006). It is unlikely that these juveniles will survive the winter due to their size and so they are more likely to be admitted to a wildlife hospital or rehabilitation centre exhibiting emaciation (Bunnell, 2001). Hedgehogs commonly enter hibernation between October and November (Pfaffle et al., 2009). Therefore, it could be argued, that the increased numbers of females during November 2015 occurred due to an increase in late litters. This is further evidenced as high proportions of males were also admitted during November 2015, potentially indicating a large amount of late litters. Conversely, during November 2016 a decreased number of both males and females were observed. This suggests that the summer litters were successful during 2016 or indicates a mild autumn season during 2015 (Bunnell, 2001). However, this cannot be confirmed as the age, weight and cause of admittance were not included for this study. To allow for greater in-depth analysis, further research including these factors is required. This would thus enable a deeper understanding of the factors affecting hedgehogs within the wild.

The lowest number of admittances, for both centres, occurred between January and March 2016. This further corresponds with the results of Bunnell (2001), who observed very low numbers of hedgehogs admitted within January and no hedgehogs admitted within February or March. During this time hedgehogs are assumed to be mid hibernation and due to awaken in March (Jackson, 2006; Jenson, 2004).

 

4.2 Gender vs. Outcome

When comparing the two centres with regards to gender influencing overall outcome, significantly more males and females were released and died at Jersey than Oak and Furrows. However, this could be suggested to occur due to Jersey having a greater admission of hedgehogs than Oak and Furrows. To improve future study when comparing data sets, ideally the samples should be of similar size so as to reduce this effect (Nakagawa and Cuthill, 2007; Bollen, 1990). This is further evidenced, as there was no significant difference between gender and outcome within the Oak and Furrows data set and within the Jersey data set. Furthermore, the number of released and dead males at Oak and Furrows were similar to those obtained from Jersey. Similar findings were seen with the available female data. Bunnell (2001) also observed no significant difference between male and female outcome, however, it was noted that survival of females was slightly greater but not significant. Therefore, mortality rates can be assumed to be equal across both genders. This is hypothesised to be because the same level of care will be given to all hedgehogs within both centres so theoretically gender should not influence the overall outcome (Molony et al., 2007).

 

4.3 Gender vs. Duration of Stay

Gender appeared to have no statistical impact on duration of stay within the individual centres and between the two centres. Hedgehogs admitted to both centres could be assumed to be of a similar health status and receiving the same level of care, so therefore, no differences may have been seen between the two centres. From the monthly data, however, differences can be seen. The longest duration of stay for females at Oak and Furrows was during September 2015 (although, this is believed to be an anomalous result). Wildlife casualties are not typically admitted for more than a few months so it is likely that this was due to an error made during data entry by either the caregiver or researcher (Trocini et al., 2008). Tribe and Brown (2000) argue that within an Australian rehabilitation centre 7% of all wildlife causalities admitted stayed for longer than 100 days. Therefore, it could be suggested, that there was no error in data entry and the hedgehogs did actually require a longer treatment period. This cannot be confirmed though,as the information on the cause of admittance was not used within this study. In addition, wildlife in Australia varies greatly compared to England so the reasons for extended staying times may be justified (Tribe and Brown, 2000).

The longest staying time within Oak and Furrows, for males and second longest for females, was during January 2015. It can be assumed those surviving animals were kept in until a spring release in March/ April, a process known as “over – wintering” (Jenson, 2004). This process is often practised by many rehabilitation centres and enables juvenile hedgehogs to gain a large amount of weight prior to release (Jenson, 2004; Robinson and Routh, 1999).  Age categories and reason for admittance were not investigated in this study, so determination of whether those admitted were due to a late breeding season is inconclusive.

The longest duration of stay for male and female hedgehogs admitted to Jersey was during October 2015. Whilst these animals weren’t in for over winter, they were still in for a large time period. This could be influenced by the reasons for the admittance or the age of these animals. Hedgehogs admitted during autumn are often emaciated or autumn juveniles (Jenson, 2004; Bunnell, 2001). If the animal reaches the desired weight before the time of hibernation then it is deemed beneficial to release the animal into the wild (Kirkwood and Sainsbury, 1996). Molony et al. (2006) found that hedgehogs kept in rehabilitation centres for greater than a month had the greatest survival rates. Therefore, even though these animals were not admitted for the entirety of winter, they were still in long enough to gain enough weight for hibernation. Survival rates post – release were not assessed during this study, due to the use of retrospective data. Suggested improvements would be to incorporate radio tracking of hedgehogs post – release to further assess the effects of rehabilitation on survival within the wild, incorporating the work of Molony et al. (2006). The recording and testing of the ages of hedgehogs may also be beneficial in future research so as to assess the impact of rehabilitation on all age categories.

 

4.4 Duration of Stay vs. Outcome

There was significant individual differences between the duration of stay and the overall outcome at Oak and Furrows and Jersey. Hedgehogs admitted to Oak and Furrows were more likely to die within the first few days of admission, as were hedgehogs admitted to Jersey. This is suggested to occur because the first few days after admittance are often the most critical for any wildlife causality and so those with the most severe injuries are less likely to survive (Mullineaux, 2014). This was supported by the survival probabilities, as hedgehogs had the lowest chance of survival on day two of admission.  The results from this study did contrast with those by Molony et al. (2007), who found no significant differences between the length of time in care and the overall outcome. Although, the cause of admission was not considered during this study. However, Molony et al. (2007) found no difference between any other intrinsic factor including; season, time of admission, age or gender. This suggests that the only indicator of survival within care is a correct clinical diagnosis, which is further highlighted by Molony et al. (2007). This may suggest that future studies could only require the cause of admission in assessing the duration of stay and outcome for an animal.

There was also a significant difference between the two centres with regards to duration of stay and outcome. However, on further breakdown of the results, the significant differences were only observed between categories not directly related. No significant differences were found between the duration of stay and released hedgehogs at Oak and Furrows and Jersey. There was also no significant differences between the duration of stay and dead hedgehogs at Jersey. This would imply that the same level of care is being provided, so the same length of time in care is needed by hedgehogs. The average duration of stay before a hedgehog can be released across both centres, appears to range between 12 to 160 days. In addition, survival chances appeared to increase after 15 days of care within both centres.

The overall success rate from both centres showed that 55.2% of all hedgehogs admitted to Oak and Furrows were released, and 54% of all hedgehogs admitted to Jersey were released. This contrasts with the findings of Molony et al. (2007) who found significant differences in success rates across four RSPCA centres. Molony et al. (2007) argue that this was due to some centres having more severe cases than others. This further suggests that the severity of cases between the centres must be consistent as the outcome rates were not affected. However, this study did not take into account the individual treatment provided. If a large proportion of individuals admitted had to be euthanised this may affect the results (Thomsen et al., 2004). Thomsen et al. (2004) analysed the mortality rates of dairy cows and found euthanasia to affect the mortality results. Euthanasia is not a reflection of poor care but is used when no other treatment option is available (Routh and Robinson, 1999). Therefore, if cause of death were to be considered for future studies, this may affect the variation in success rates for centres.

 

5.0 Conclusion

Overall, this study found both centres to have successful release rates, indicating rehabilitation centres to improve the prognosis of sick and injured animals. The length of time spent within both centres was shown to affect the outcome of hedgehogs, with the greatest duration of stay occurring over the winter period. This is indicated to occur due to “over-wintering” practices from the rehabilitation centres. The lowest chances of survival were shown to occur after two days of admittance, whilst the chances of release were greatly improved after 15 days. This is suggested to be due to hedgehogs dying of the most severe injuries within the first few days. Male hedgehogs were admitted more than females, with peak admittances occurring in the summer and autumn seasons, and this is suggested to relate to the breeding seasons. No significant differences were found, however, between gender and survival outcome or duration of stay. This would suggest mortality rates to be equal across both genders. To further improve this study, consideration of age, weight, injury, illness, cause of death and reason for admittance should be considered, so as to better enable the understanding of factors affecting admittance. The use of radio-tracking and monitoring of survival post – release may also be beneficial in understanding the benefits of wildlife rehabilitation.

 

References

Ashraf, N. V. K. and Menon, V. (2005) Problems and Prospects of Rehabilitating Wildlife Displaced due to Man—Wildlife Conflict and the Wildlife Trade in India. Back to the Wild: Studies in wildlife Rehabilitation. New Delhi: Wildlife Trust of India [online]. pp. 34 – 44. [Accessed 28 February 2017].

Baker, P. J. and Harris, S. (2007) Urban mammals: what does the future hold? An analysis of the factors affecting patterns of use of residential gardens in Great Britain. Mammal Review [online]. 37 (4), pp. 297-315. [Accessed 07 February 2017].

Bollen, K. A. (1990.) Overall fit in covariance structure models: Two types of sample size effects. Psychological Bulletin [online].107 (2), p.256. [Accessed 10 February 2017].

Bullen, K. (2013) Care and treatment of hedgehogs (Erinaceus europaeus). Veterinary Nursing Journal [online]. 28 (2), pp. 54 – 57. [Accessed 02 March 2017].

Bunnell, T. (2001) The Importance of Faecal Indices in Assessing Gastrointestinal Parasite Infestation and Bacterial Infection in the Hedgehog Erinaceus europaeus. Journal of Wildlife Rehabilitation [online].  24 (2), pp.13 – 17. [Accessed 07 February 2017].

Delaney, D. G., Sperling, C. D., Adams, C. S. and Leung, B. (2008) Marine invasive species: validation of citizen science and implications for national monitoring networks. Biological Invasions [online]. 10 (1), pp.117-128. [Accessed 24 February 2017].

Department of Environment, Food and Rural Affairs (2011) Biodiversity 2020 [online]. London: Nobel House. (PB 13583). Available from: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/69446/pb13583-biodiversity-strategy-2020-111111.pdf. [Accessed 11 October 2016].

Dowding, C. V., Harris, S., Poulton, S. and Baker, P. J. (2010) Nocturnal ranging behaviour of urban hedgehogs, Erinaceus europaeus, in relation to risk and reward. Animal Behaviour [online].  80 (1), pp. 13 – 21. [Accessed 10 October 2016].

Elliott, A. C. and Hynan, L. S. (2011) A SAS® macro implementation of a multiple comparison post hoc test for a Kruskal–Wallis analysis. Computer methods and programs in biomedicine [online].102 (1), pp.75-80. [Accessed 23 January 2017].

Gaglio, G., Allen, S., Bowden, L., Bryant, M. and Morgan, E. R. (2010) Parasites of European hedgehogs (Erinaceus europaeus) in Britain: epidemiological study and coprological test evaluation. European journal of wildlife research [online]. 56 (6), pp.839-844. [Accessed 11 November 2016].

Goel, M. K., Khanna, P., Kishore, J. (2010) Understanding survival analysis: Kaplan-Meier estimate. International Journal of Ayurveda Research [online]. 1 (4), pp. 274-278. [Accessed 26 February 2017].

Grogan, A. and Kelly, A. (2013) A review of RSPCA research into wildlife rehabilitation. Veterinary Record [online]. 172, pp. 211 – 214. [Accessed 15 October 2016].

Hof, A. R. and Bright, P. W. (2010) The value of agri-environment schemes for macro-invertebrate feeders: hedgehogs on arable farms in Britain. Animal Conservation [online]. 13 (5), pp. 467 – 473. [Accessed 04 October 2016]

Hof, A. R. and Bright, P.W. (2016) Quantifying the long-term decline of the West European hedgehog in England by subsampling citizen-science datasets. European Journal of Wildlife Research [online]. pp. 1-7. [Accessed 20 October 2016].

Hubert, P., Julliard, R., Biagianti, S. and Poulle, M. L. (2011) Ecological factors driving the higher hedgehog (Erinaceus europeaus) density in an urban area compared to the adjacent rural area. Landscape and Urban Planning [online]. 103 (1), pp. 34 – 43. [Accessed 07 February 2017].

Irvine, R. J. (2006) Parasites and the dynamics of wild mammal populations. Animal Science [online].  82 (6), p.775. [Accessed 08 February 2017].

Jackson, D. B. (2006) The breeding biology of introduced hedgehogs (Erinaceus europaeus) on a Scottish Island: lessons for population control and bird conservation. Journal of Zoology [online]. 268 (3), pp. 303 – 314. [Accessed 27 February 2017].

Jackson, D. B. (2007) Factors affecting the abundance of introduced hedgehogs (Erinaceus europaeus) to the Hebridean island of South Uist in the absence of natural predators and implications for nesting birds. Journal of Zoology [online]. 271 (2), pp. 210 – 217. [Accessed 04 October 2016].

Jensen, A. B. (2004) Overwintering of European hedgehogs Erinaceus europaeus in a Danish rural area. Acta theriologica [online]. 49 (2), pp.145 – 155. [Accessed 01 March 2017].

Joint Nature Conservation Committee (2016) Joint Nature Conservation committee. Available from: http://jncc.defra.gov.uk/page-5170 [Accessed 06 October 2016].

Kirkwood, J. K. and Sainsbury, A. W. (1996) Ethics of interventions for the welfare of free-living wild animals. Animal Welfare [online]. 5, pp. 235-244. [Accessed 22 February 2017].

Martínez, J. C., Rosique, A. I. and Royo, M. S. (2014.) Causes of admission and final dispositions of hedgehogs admitted to three Wildlife Rehabilitation Centers in eastern Spain. Hystrix, the Italian Journal of Mammalogy [online]. 25 (2), pp.107 – 110. [Accessed 06 February 2017].

Molony, S. E., Baker, P. J., Garland, L., Cuthill, I. C. and Harris, S. (2007) Factors that can be used to predict release rates for wildlife casualties. Animal Welfare [online]. 16 (3), p.361. [Accessed 25 February 2017].

Molony, S. E., Dowding, C. V., Baker, P. J., Cuthill, I. C. and Harris, S. (2006) The effect of translocation and temporary captivity on wildlife rehabilitation success: an experimental study using European hedgehogs (Erinaceus europaeus). Biological Conservation [online]. 130 (4), pp. 530-537. [Accessed 02 February 2017].

Mullineaux, E. (2014) Veterinary treatment and rehabilitation of indigenous wildlife. Journal of Small Animal Practice [online]. 55 (6), pp. 293 – 300. [Accessed 27 February 2017].

Nakagawa, S. and Cuthill, I. C. (2007) Effect size, confidence interval and statistical significance: a practical guide for biologists. Biological Reviews [online]. 82 (4), pp.591-605. [Accessed 23 February 2017].

Pavlović, I. and Savić, B. (2016) Helminth fauna of the northern white-breasted hedgehog (Erinaceus roumanicus) in Serbia. Journal of Parasitic Diseases [online]. pp.1 – 2. [Accessed 09 February 2017].

Peoples Trust for Endangered Species (PTES) (2015) Peoples Trust for Endangered Species. Available from: https://ptes.org/wp-content/uploads/2015/11/Conservation-strategy-for-the-hedgehog-in-the-UK-2015-2025.pdf [Accessed 04 October 2016].

Peoples Trust for Endangered Species (PTES) (2015) Peoples Trust for Endangered Species. Available from: https://ptes.org/wp-content/uploads/2015/11/Conservation-strategy-for-the-hedgehog-in-the-UK-2015-2025.pdf [Accessed 04 October 2016].

Pfäffle, M., Petney, T., Elgas, M., Skuballa, J. and Taraschewski, H. (2009) Tick-induced blood loss leads to regenerative anaemia in the European hedgehog (Erinaceus europaeus). Parasitology [online]. 136 (4), pp.443-452. [Accessed 07 February 2017].

Pyziel, A. M. and Jeżewski, W. (2016) Coprology of a single Northern white-breasted hedgehog (Erinaceus roumanicus): first report of Isospora rastegaievae in Poland. Acta Parasitologica [online]. 61 (3), pp. 636 – 638. [Accessed 09 February 2017].

Razali, N. M. and Wah, Y. B. (2011) Power comparisons of shapiro-wilk, kolmogorov-smirnov, lilliefors and anderson-darling tests. Journal of statistical modeling and analytics [online]. 2 (1), pp. 21 – 33. [Accessed 28 January 2017].

Reeve, N. J. (1998) The survival and welfare of hedgehogs (Erinaceus europaeus) after release back into the wild. Animal Welfare [online]. 7, pp.189 – 202. [Accessed 12 February 2017].

Rich, J. T., Neely, J. G., Paniello, R. C., Voelker, C. C. J., Nussenbaum, B. and Wang, E, W. (2010) A Practical Guide to Understanding Kaplan-Meier Curves. Otolaryngology–head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery [online]. 143 (3), pp. 331-336. [Accessed 26 February 2017].

Robinson, I. and Routh, A. (1999) Veterinary care of the hedgehog in practice. London British Veterinary Association [online]. 21, pp. 128 – 138. [Accessed 06 February 2017].

Rondinini, C. and Doncaster, C. P. (2002) Roads as barriers to movement for hedgehogs. Functional Ecology [online].16 (4), pp.504-509. [Accessed 27 February 2017].

Roos, S., Johnston, A. and Noble, D. (2012) UK Hedgehog Datasets and their Potential for Long – Term Monitoring. The British Trust for Ornithology [online]. Available from: https://www.bto.org/sites/default/files/u12/hedgehogscopingreportfinal05042012ptes.pdf [Accessed 06 February 2017].

Royal Society for the Protection of Birds (RSPB) (2010) The RSPB annual Review 2009 – 2010 [online]. Available from: https://www.rspb.org.uk/Images/Annual_review_tcm9-261508.pdf. [Accessed 06 February 2017].

Silaghi, C., Skuballa, J., Thiel, C., Pfister, K., Petney, T., Pfäffle, M., Taraschewski, H. and Passos, L. M. F. (2012) The European hedgehog (Erinaceus europaeus) – A suitable reservoir for variants of Anaplasma phagocytophilum? Ticks and Tick-borne Disease [online]. 3 (1), pp. 49 – 54. [Accessed 04 October 2016].

Silvertown, J. (2009) A new dawn for citizen science. Trends in ecology & evolution [online]. 24 (9), pp.467-471. [Accessed 24 February 2017].

Simpson, V. R. (2002) Wild animals as reservoirs of infectious diseases in the UK. The Veterinary Journal [online].163 (2), pp.128-146. [Accessed 08 February 2017].

Skuballa, J., Taraschewski, H., Petney, T. N., Pfäffle, M., and Smales, L. R. (2009). The avian acanthocephalan Plagiorhynchus cylindraceus (Palaeacanthocephala) parasitizing the European hedgehog (Erinaceus europaeus) in Europe and New Zealand. Parasitology Research [online]. 106 (2), 431-437. [Accessed 09 October 2016].

Thomsen, P. T., Kjeldsen, A. M., Sørensen, J. T. and Houe, H. (2004) Mortality (including euthanasia) among Danish dairy cows (1990–2001). Preventive veterinary medicine [online]. 62 (1), pp.19-33. [Accessed 25 February 2017].

Toms, M. P. and Newson, S. E. (2006) Volunteer surveys as a means of inferring trends in garden mammal populations. Mammal Review [online]. 36(4), pp. 309-317. [Accessed 23 February 2017].

Tribe, A. and Brown, P. R. (2000) The role of wildlife rescue groups in the care and rehabilitation of Australian fauna. Human Dimensions of Wildlife [online]. 5 (2), pp.69-85. [Accessed 21 February 2017].

Trocini, S., Pacioni, C., Warren, K. and Robertson, I. (2008) Wildlife disease passive surveillance: the potential role of wildlife rehabilitation centres. Proceedings of the national wildlife rehabilitation conference [online]. pp. 1 – 5. [Accessed 07 February 2017].

Wembridge, D and Langton. S. (2016) Living with Mammals: An Urban Study. British Wildlife [online]. 27 (3), pp. 188 – 195. [Accessed 16 October 2016].

Wembridge, D and Langton. S. (2016) Living with Mammals: An Urban Study. British Wildlife [online]. 27 (3), pp. 188 – 195. [Accessed 16 October 2016].

Wembridge, D. (2011) The State of Britain’s Hedgehogs. The Peoples Trust for Endangered Species [online]. Available from: http://ptes.org/wp-content/uploads/2014/06/SOBH2011lowres.pdf [Accessed 07 February 2017].

Williams, R. L., Stafford, R. and Goodenough, A. E. (2015) Biodiversity in urban gardens: Assessing the accuracy of citizen science data on garden hedgehogs. Urban ecosystems [online]. 18 (3), pp.819 – 833. [Accessed 24 February 2017].

Young, R. P., Davison, J., Trewby, I. D., Wilson, G. J., Delahay, R. J. and Doncaster, C. P. (2006) Abundance of hedgehogs (Erinaceus europaeus) in relation to the density and distribution of badgers (Meles meles). Journal of Zoology [online]. 269 (3), pp. 349-356. [Accessed 08 February 2017].