Volume 4 Pages 1 - 45 (March 1989)

Citation: Williams, J. (1989) Blindness in Otters IUCN Otter Spec. Group Bull. 4: 29 - 30

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Blindness in Otters

James Williams

Stoford Manor, West Buckland, Wel1ington, Somerset, TA21 9LS

Blind otters appear to have been relatively common in Great Britain during a period which coincided with their decline in numbers or even total disappearance in many areas. I first became interested after encountering three blind otters myself, and decided to run a small investigation to try to find out the extent of the problem. The three otters I encountered were all in the same area of England, and two were the same river system, but chance remarks led me to suspect that this form of blindness might be occurring in other areas as well. The first otter was a full grown adult which used regularly to hunt eels in daytime in the shallow waters of Leighton Moss, a large reedbed with lagoons well known as a wildfowl reserve. It hunted with two other otters, and appeared equally proficient, although both its eyes were completely white and apparently opaque. I assumed that this indicated blindness. This was confirmed when I saw two otters fail to evade a clearly 'visible' hound during hunts; one was opaque in both eyes, the other only in one. All three appeared in strong condition, although one had a major infestation of sheep ticks, a not uncommon occurrence in the northern hills.

My method was to appeal to anybody I thought might have such knowledge. I wrote letters to the main sporting periodicals asking for help, and I contacted personally as many people as possible. These could be summarised in three categories; those who frequently followed the packs of organised otterhounds to be found in most areas of Britain in those days, fishermen and casual naturalists, and those fully employed in surveying the otter population. All were very willing to help.

They gave me details of 26 blind otters, of which three were of little interest as they had been shot in the head. The rest all seemed to have the same sort of obviously visible milky white opaqueness except for one road casualty, which had one eye which had never unsealed after birth. Two were blind in one eye only, and one was described as  'nearly blind'. One which was blind on one side only was approached as it sat beside a noisy Scottish burn and prodded with a stick, when it made an alert and agile escape. Even those which were hunted by hounds seemed well able to cope in the water. So although many of the otters reported to me had been found dead or near death, there were sufficient instances of healthy but blind otters for it to appear certain that the blindness itself was not necessarily a direct cause of death. It is in fact entirely possible that the first otter that I saw in Leighton Moss was the same individual that was found dying there exactly ten years later having lived a full lifespan. Unfortunately we shall never know.

Ten of the twentytwo were described as in good condition.  However three were in a very poor state; one was described as 'starving' and the other two were in fact dying from liver disorders. One was a very old otter indeed, so his reaching such an age can be counted as a plus than a minus, but the other was a young dog which should have been in his prime.  Why he should not be coping as well as others in a similar plight would be perhaps knowledge of some conservational value. An even younger otter, quite a small cub, seemed perfectly fit despite its blindness although it would not have to catch its own prey.

Geographically there was a wide distribution; the records came from eleven different counties, although the most were from the South. The distribution of the cases in time may perhaps be more significant. The earliest record was in 1957, and cases occurred fairly regularly until 1971. They then became more infrequent, but there were three in 1980. In 1966 there were also three. There is only one instance of two cases from the same place at the same time, in 1959, on the River Itchen. So an epidemic or infectious disease seems unlikely to be the cause, more especially as several of the reports told of other apparently normally sighted otters living with the blind one.

But try as I might I could find no earlier records or rumours of a blind otter than 1957. I think this must be significant; 22 cases between 1957 and 1980, but none in the previous 800 years, which is the time that the pastime of otterhunting has been recorded in England. There is much literature about this sport, and many books recording the peculiarities of wildlife as sportsmen found them; they would certainly have recorded it if they had found a fit but blind otter. The recent generations of hunters seem to have been great diarists, and the hunts kept full and detailed records. That not one such case came to light must, in my opinion, make this a modern problem, and therefore probably of some indirect significance in the dramatic decline of the population of otters in Britain at that time. The fall-off in cases in the eighties is to be expected: there were by then far fewer otters. It is a great pity that only three of the twenty which were dead got into qualified hands for a proper post-mortem. An opportunity to learn much has been lost.

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