The main purpose of this study was to examine the presenting signs of grey seal pups found during the initial admission examination. Presenting signs reported in this study, in order of prevalence, are: trauma, respiratory disorders, ocular disorders, malnourishment, oral disorders and onychia.
There was a dramatic difference in the hospitalisation time between seals that were released and those that did not survive. Examination of the survival plot shows that the majority of seals that did not survive died while in the early stages of rehabilitation. This suggests that there could be a critical period during early rehabilitation which could affect the long term outcome of the intervention. This could also indicate that current methods of long term rehabilitation are sufficient to ensure a high survivorship.
Over 80% of the seal pups had one form of trauma. The high level of trauma suggests that rehabilitation centres in the UK need to be prepared to care for wounded seals. With the recent discovery of Mycobacterium bovis
in a non-healing wound [15
] and the high prevalence of puncture wounds (68.78%), rehabilitators should be aware of the potential zoonotic risks and take appropriate protective measures when dealing with infected non-healing wounds.
Grey seal pup admission into the rehabilitation centre was seasonal. The pup production season in south-west England is mid-August through December, with the peak production occurring between August and October [1
]. Admission counts peaked in November. This study found the majority of pups rehabilitated were moulted (Table 1
). Pups remain on shore with their mothers until weaned at approximately 3–4 weeks of age. Rescuers are trained not to rescue a seal pup when the mother is present unless the pup has suffered serious trauma or illness [18
]. After weaning and moulting, grey seal pups either enter into the water immediately or stay on land for up to a month [1
]. Thus shift in the seasonality of seal admissions from pup production would not be unexpected. Non-moulted pups admitted after pup production had ended (e.g., February, March, April, May) may have been pups born post-pup production season. Alternatively, there could be delayed moulting in ill pups. Further investigation into non-moulted pups outside of pup production season is needed.
This study found that 42% of rehabilitated seals presented with hyperthermia. Grey seals spend a majority of their time in the sub-arctic waters of the north Atlantic [1
]. Their adapted physiology, used to cope with the cold water, makes them highly susceptible to overheating. Thus, it is expected that a large percentage would present with hyperthermia. Rehabilitation centres should be prepared to treat for hyperthermia.
This study found a significant relationship between age and respiratory conditions. Older seal pups showed increased respiratory signs. A similar relationship with age was found with puncture wounds, oral and nasal disorders. In addition, females were less likely to have abrasions, oral, and respiratory lesions. The reasons behind these relationships are unknown, and suggest further areas of research.
Respiratory disorders increased with age. Unfortunately, this retrospective study was unable identify the cause of the respiratory disorders seen in the pups. However, Baker et al.
] found an increase in pulmonary nematode parasitism in older seals, suggesting a possible cause of the increased odds of respiratory disorders in older pups. Further investigations, including tests for pulmonary nematode infestations in grey seal pups, is required.
Nasal disorders had a similar relationship to respiratory disorders. 50% of white-coat pups that presented with nasal disorders also had a respiratory disorder. This suggests that the nasal discharge observed was most likely caused by a lower respiratory tract lesion. However, this relationship was not observed with moulted pups. Naso-pharyngeal mites (Halarachne halichoeri
) and symptomatic signs have been found in high prevalence in juvenile grey seals along the Spanish coastline [20
]. Thus, it is possible that lower respiratory tract issues are more likely the cause of younger pup nasal discharge, while older pups are more likely to have an upper respiratory tract issue such as Naso-pharyngeal mites.
Puncture wounds were less likely to be found on younger pups. Puncture wounds can be caused by intraspecific interactions, predator/prey interactions, and anthropogenic causes. However, a recent study found 55% free ranging grey seal pups on a breeding beach colony had puncture wounds [21
]. This suggests that intraspecific interactions are the most likely cause for puncture wounds; the seal pups had the wounds when anthropogenic and predator causes were unlikely.
Oral lesions found in this data were mostly oral ulcers. Streptococcus equi
, has been associated with oral ulcers in the past [19
]. It has also been suggested that oral ulcers in the grey seal pup could be due to changes in the gingiva during tooth eruption [2
]. Our study found older seal pups were more likely to have oral ulcers, indicating that the effect of tooth eruption could be a valid possibility. No cultures of the oral lesions were performed in this study, and thus the causative agent of the ulcers could not be determined. Further investigations need to be performed to rule out other causative agents (e.g., azotaemic, viral, or autoimmune ulcers).
It should be noted that only moulted pups had netting injuries, though the total number was low. A fishers exact showed a possible significance in this proportion, but a larger sample size is needed for rare events. Grey seal exposure to nets typically occurs in water. Only older, weaned grey seal pups enter into open water by their own choice [10
]. Thus, it would be expected that only older pups would have netting injuries. Further research is needed to determine if this association holds to the expectation.
There was a large difference between the prevalence of ocular disorders in this study compared to those of Barnett et al
]. The ocular lesions noted were similar other lesions observed by Barnett et al
]. This study found 46.34% of seal pups had an ocular condition (e.g., corneal oedema, corneal ulceration, etc.
) while in the previous study only 13% had an ocular lesion. Grey seals have large eyes, and these eyes are highly susceptible to trauma [11
], which could explain the high prevalence of ocular conditions in pups presented for rehabilitation. The reason behind the difference in the studies is unknown, and should be considered by future research.
Malnourishment was found in 42.63% of seal pups, in comparison to 71% observed by Barnett et al.
]. A study on grey seal mortality found that starvation was the highest probable cause of death in older juveniles [19
]. The difference is likely due to different methods used to define malnourishment. This retrospective study relied on the subjective BCS, while Barnett et al.
] used weights and muscle mass cover and Baker et al.
] used post mortem information. The BCS was not standardised before the study, and thus may have caused an under-reporting of malnourished prevalence. Alternatively, the use of weight in sick animals to assess nutritional status may have caused an over-estimation of the malnourished prevalence in Barnett et al.
]. In addition, weight of the pup might reflect the age of the mother instead of the nutritional status of the pup [22
]. Further research is needed to determine the true malnourishment prevalence.
There were some limitations to this study due to its retrospective nature. The examination of the seals was not standardised and the examiner on admission was not noted in the record, thus inter-observer reliability could not be assessed. In addition, this study performed multiple comparisons and increased the familywise error rate. However, due to the nature of this exploratory epidemiological survey and the data, no multiplicity adjustment is required [23
]. Confirmatory studies for this study’s findings with appropriate controls should be performed in the future.