THE SUFFOLK OTTER SURVEY The findings of a three-year survey RODNEY B . W E S T
THE rivers, meres and marshlands of the Suffolk countryside have for thousands of years provided the Common Otter (Lutra lutra) with conditions ideally suited to its life-cycle. Although remains of extinct Lutrinae have been found dating from various periods in the Pleistocene, our present otter's ancestors probably returned to the Suffolk waterways, in the wake of the last retreating icecap some 10,000 years ago. The private life of the otter is still very much a mystery. Its crepuscular habits and secretive nature have proved a daunting obstacle to any study. Even the animal's general distribution and the size of its population on particular rivers has not been systematically researched in this country. Using these last two points as its principle objective, this survey has attempted to record the otter's present status in the county of Suffolk. Also something of its past distribution is noted and certain recommendations for the animal's continuing conservation are given. Methods The problem of trying to collect sufficient information relevant to otter distribution in Suffolk was approached in two ways. Initially an appeal was made in May, 1969, to people who, it was thought, would be prepared to keep under surveillance selected sections of river or marsh. In these chosen areas the intention was that each individual surveyor would record any evidence of otter activity. This was achieved by the surveyor making periodic Visits to the particular site and searching for typical otter signs, i.e. pad-marks or fresh spraint spots. All available information was written on a Record Card, this included: time and duration of visit, weather, area under study and a description of anything found. Although this approach formed the basis of the survey, information was also requested from anyone whose daily routine might bring them into contact with Otters, this included: Ministry of Agriculture officials, coypu trappers, River Board personnel and gamekeepers, etc. Finally the author has tried to fill in as many outstanding areas as possible during the length of the survey. Results Sufficient information is available to allow for a reasonably detailed analysis of the otter's distribution. The principle river systems have been divided into 12 sections and each dealt with in turn. All the results taken from the Record Card returns are gathered together in Table I.
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(1) T H E RIVER STOUR including the R. Box and R. BRETT The River Stour delineates along much of its length the southern boundary of Suffolk and it serves the same purpose for the Suffolk Otter Survey. Many areas of the Stour have suffered from riparian disturbance during the past decade. The river around Dedham appears to have contained otters up until 1967 but growing disturbance brought about by greater recreational use of the river must be a contributory factor in the animal's disappearance along the lower half of the river. One animal was seen in September, 1970, on the northern side of the estuary around Holbrook. It stayed in the area for several days, where it frequented the outlet of a small stream which led into the estuary. During the winter of 1971 and the spring of 1972, otter activity was found both on the River Brett and the River Box, two small tributaries of the Stour. The only other definite area known to hold otters is between Lamarsh and Sudbury, where a sympathetic landowner leaves the whole of his sizeable riverside boundary overgrown and undisturbed. ( 2 ) T H E RIVER G I P P I N G / O R W E L L
Along the entire length of the Gipping/Orwell, no evidence of otter occupation was found throughout the period of the survey. The amount of pollution and bank-side disturbance again appears to have influenced the animal's disappearance. It is a point of conjecture just when the otter became extinct on the Gipping. Individuais were seen in 1955 and there are several earlier reports including an incident when a dog otter was killed in Holywells Park, Ipswich. The evidence seems to point to the fact that otters were absent from this river before the widespread decline during the 1960s. ( 3 ) T H E RIVER D E B E N
The River Deben is one of the few well 'otter populated' rivers in Suffolk. The survey's findings indicate that at least one animal works the area towards the mouth of the Deben including the Ramsholt Marshes, nothing has been found however on the Kirton side. It is probably this animal's territory that stretches as far as the Alderton Marshes and therefore necessitates a crossing of the Alderton Road. This has proved a hazardous undertaking for the individuals involved. A dog otter was reported killed in March, 1972, at a spot where a stream is piped under the road. Another animal was killed at the same place in January, 1973. The corpse of the 1972 animal was examined and showed an otter in good condition weighing approximately 9.0 kg. and measuring 1123 mm. from nose to tip of tail. An earlier report of another otter killed on the same road was in January, 1962. This animal was a female and measured 1114 mm. from nose to tip of tail.
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Above Wilford Bridge indications are that there are two or three separate territories. Although they have not been accurately defined, Otters are known to travel as far up the river as Cretingham. One animal successfully reared two young on the Mill Pond at Campsea Ashe in 1968. (4) T H E RIVER A L D E / O R E including the BUTLEY RIVER T h e area around the mouth of the Ore, the adjacent marshes and the Butley River are known to incorporate at least one otter territory. Tracks are also found at irregulär intervals on Havergate Island suggesting that the Island is not within the home ränge of any one individual but is an outlying haunt that is visited infrequently. Above Orford little has been found on the Sudbourne Marshes, although a group of three Otters was seen in December, 1969, at Slaughden. On the Aide, otter activity is found around Langham Bridge and as far up river as Stratford St. Andrew. Tracks and spraint spots are regularly found on the Iken Marshes. T h e upper reaches of the Aide have not been covered so it is impossible to say how far up river Otters might be. (5) THORPENESS MEARE including the HUNDRED RIVER Otters are resident on the Hundred River and 'The Fens', an area of reed-beds providing excellent cover. Spraint, footprints and remains of meals are regularly found along the Hundred River. T h e Meare itself appears to be rarely visited, possibly its use as a boating lake is an influence on this. (6)
MINSMERE
T h e R.S.P.B. Nature Reserve and the attendant Minsmere River, are the home territories of one, possibly two, Otters. Field signs in the way of spraint and footprints are found throughout the year. Young Otters with accompanying adults have been seen in most years during the past decade. Mr. H. E. Axell, R.S.P.B. Warden, caught a dog otter in one of his coypu traps on 20th February, 1971. It measured 890 mm. overall and weighed 5 kg. After its release, footprints continued to be seen in the usual places and so it was presumed it was none the worse for its experience! ( 7 ) T H E WALBERSWICK MARSHES
T h e Walberswick Marshes are not, it appears, included in the resident territory of any otter and of all the coastal marshes this area remains a blank. This seemingly paradoxical Situation has received close study during the length of the survey. Yet only once for a period of a few weeks between October and December,
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1970, was there any otter activity found. Miss Elaine Hurrell (priv. comm.) was very familiar with the otter's use of the Walberswick Marshes during the late 1950s and early 1960s. At this time she found the whole area frequented by otters with many sprainting spots, slides and runs. Miss Hurrell visited the Marshes again in 1971 and 1972 and after a close study she could only confirm the survey's own findings. The Walberswick Marshes and its environs have recently been declared a National Nature Reserve, so it is hoped that with the land management biased towards wildlife, the otter will soon return. ( 8 ) T H E RIVER BLYTHE
Very little activity of otters is found more than 2 km. above Blythburgh, this is probably due in part to the bankside clearance. Otters appear to favour the Wang, a small tributary of the Blythe, and most of the 'flooded' sector of the river between Blythburgh and Reydon Marshes. ( 9 ) EASTON, COVEHITHE AND BENACRE BROADS AND KESSINGLAND LEVEL
Spraint and padmarks have been found in all four of these areas during the three years of the survey, although sometimes at very irregulär intervals. Without intensive study in this section it would be unwise to postulate how many territories are involved. The size of the area points to either one or two individual territories, at least one animal moves between Kessingland Level and Benacre Broad as one was disturbed from the path leading to the Level. ( 1 0 ) T H E RIVER WAVENEY
T h e River Waveney is, from its source in the Redgrave Fens to its confluence with the River Yare at Breydon Water, over 90 kms. in length. Of this only 15 kms. have been subject to investigation, it is therefore very likely that some otters have been missed. This is an unfortunate Situation, as the river is probably in a transitional stage regarding its otter population, receiving as it does a growing volume of rnotor cruiser traffic. Otters are known to inhabit still these areas; T h e Oulton Marshes and the western end of Oulton Broad, the Herringfleet Marshes where tracks were found in the snow. Also in the Weybread area of the Waveney there is known to be at least one animal. There is probably an individual along the Hoxne Stretch where spraint and indistinct footprints have been found. No otter regularly haunts the last few kilometres of the river above Diss, although sporadic activity is noted at Redgrave and Redgrave Lake.
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( 1 1 ) T H E L I T T L E OUSE
T h e Little Ouse also has its source in the Redgrave Fens but then winds its way westward through country that was formerly Breckland. This is another good 'otter river' with at least two Otters known to be between Euston and Bio' Norton. There is some unsubstantiated evidence suggesting that Otters travel across country between the Little Ouse around Rushford and the River Thet at Shadwell Park. T h e distance involved is just under 2 kilometres, and it should be noted that Otters have been seen further away from water than this. Signs of Otters have been found above Thetford to as far as Brandon, and again between Brandon and Hockwold. T h e river was covered past Hockwold to the county boundary but nothing was found although the river could well hold Otters for it is good habitat with thick bank-side Vegetation. ( 1 2 ) T H E RIVER LARK
T h e River Lark was known to contain Otters during the early 1960s particularly between Cavenham and West Stow. One was shot by a gamekeeper in 1965 but after this date there have been no other reports of Otters. Information collected during the period of the survey points to a very depleted population. And although no definite evidence was forthcoming, informants who work on the river say there are still Otters around Lackford. Discussion Although a reasonably composite picture has emerged to reveal the otter's present status in Suffolk, the survey's findings do need some qualification. Because of anomalies inherent in the survey's methods, its results are not presumed to be conclusive. Principle among these sources of error was the failure to achieve complete coverage of all suitable otter habitat. Also it was impossible to synchronise the surveyors visits so that a single otter was not recorded twice. And also the problem of discrepancies between individual surveyors as to what was and what was not evidence. It was apparent therefore that no absolute figures for the total otter population would be obtained. T h e alternative is a fairly well-informed estimate, which when compared with the paucity of such figures in the past, will be seen to have some value. Erlinge, in his study of Otters in Southern Sweden (Erlinge, 1968), gives the mean size of an otter territory as being approximately 10 kms. in length. Some caution must be used when applying these figures to Suffolk, where diiferences in topography may infiuence the territory size. A comparison here would be of value. T h e Deben for present purposes, it is presumed, is a well-stocked river. Upwards of 40 kms. of its length may be
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expected to hold otters. This would indicate that there was adequate habitat for three to five otter territories. Research between 1970 and 1972, although again not conclusive, tended to point to three territories with possibly a fourth. This roughly agrees with Erlinge's work and it would therefore be reasonable to assume that a density of one otter per 10 kms. of river was a good average for Suffolk, though the marshes may contain higher numbers. Listed below in TABLE 2 are the 12 categories given in the Results section. In brackets are given the number of otters thought at present to be in these areas. These figures have at least a 25 % tolerance. It is unfortunate that no previous figures are available which would allow for a comparison. It is therefore impossible to say if the present status of the otter is the Optimum or merely a vestigial population. Old hunt returns and other references for the period 1870 to 1940, seem to show that otters were being found on almost every river in the county. Ticehurst, 1932, appears to confirm this when he says, "There is hardly a suitable stream and certainly no Broad in the county that lacks otters". Probably the status quo was maintained until the late 1940s but from that date there appears to have been a steady downward trend in some areas. A number of factors have contributed to the otter's decline and chief among these must be counted river pollution and disturbance. Disturbance is something that has been increasing for the past quarter of a Century. But recent years have seen an upsurge in such activities as pleasure boating and freshwater angling, to a point where previously inaccessible backwaters are now receiving the attention of public pressure. T h e present practise of Clearing away all bankside Vegetation, in an effort to improve the river's flow, is a serious encroachment on surviving otter habitat. Excessive disturbance has serious repercussions for the otter. If a river contains several stretches of disturbed habitat it has the effect of fragmenting the otter territories and irtipeding the movement of individuals along the river. Otters are very reluctant to pass through long stretches of river devoid of Vegetation cover, and their tolerance of areas subject to intensive human pressure is very small. If this Situation persists on a river, otter territories become contracted, and casualties cannot be replaced in the normal way, ultimately the river loses its otters. It is probably this process that is responsible for the loss of otters on rivers like the Gipping and the Lark. Today it can be seen in progress on rivers such as the Waveney and the Stour. One of the projected aims of this survey was, if it proved feasible, to put forward suggestions for conservation measures.
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In retrospect, more Otters have been located than were first thought to be present in the spring of 1969. This does not allow for a feeling of complacency for many areas are under growing pressure and the Situation is liable to very sudden change. T o gain some insight as to which areas are most effected, an arbitrary grouping has been made in T A B L E 3. All the 12 areas have been placed in three columns. Column one EXTINCT gives the areas where Otters are no longer found and where no resident territories exist. Column two ENDANGERED lists the areas which are at present under the greatest pressure and Column three VIABLE gives the areas which hold good otter populations and are at present regarded as safe. T h e success of any policy designed to protect Otters on a river will be dependant on discussions leading ultimately to the approval and co-operation of the riverside landowners, River Board authorities, gamekeepers and any other relevant bodies, i.e. Angling societies, Eastern Counties Otter Hounds, etc. A working framework for any such discussions should include such desirables as: (a) T h e conducting of an ecological study of the proposed area and its environs. This would probably illuminate the problem areas as well as providing valuable information. (b) T h e possibility of leaving parts of the main river and adjacent areas such as feeder streams, relatively free of human disturbance. (c) T h e need to retain bank-side Vegetation wherever possible. (d) Providing information for gamekeepers and others, which would aid correct identification of the otter. It would probably be wise to concentrate on the present viable areas listed in Column three initially. Reasonable success and experience gained, would then allow efforts to be focused on the more difficult areas listed in Column two. In these areas the possibility of re-introducing the otter could also be explored. In conclusion, this survey has tried to ascertain the present status of the otter in Suffolk, it provides also a reliable basis for comparison in the event of any future study. Its findings show that some areas still hold viable populations, others appear to be in the balance, while a few areas are at present devoid of otters. If the present Situation is to be stopped from deteriorating any further, some practical action is needed. It is the responsibility of the enlightened among us to precipitate such action as is appropriate. Most people have never seen an otter during their lifetime, yet there is some aesthetic pleasure to be gained in the knowledge that this animal is left free to travel the Suffolk waterways, as it has done since man huddled in caves for protection.
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Acknowledgements This survey would not have been possible without the work and enthusiasm of the field recorders. I would like to take this opportunity of thanking them all for the work they put in, over the three-year period. They are as follows : M r . J. A. Abbott, Fiatford Mill Field Studies Centre. (River Stour.) Mr. H . E. Axell, Minsmere. (R.S.P.B. Minsmere.) Mr. F. Royle-Bantoft, Woodbridge. (Butley River.) Mr. I. M . Barratt, Ipswich. (River Deben.) M r . G . B. G . Benson, Southwold. (Benacre and Easton Broad.) M r . R. S. Briggs, Oulton Broad. (Oulton Broad.) Mrs. B. G . Brocklebank, Higham. (River Brett.) M r . and Mrs. E. Bunch, Walberswick. (Walberswick Marshes.) Mr. M . Cavanagh, Hollesley. (Barthorpes Creek.) Mr. and M r s . H . E. Chipperfield. (River Blythe.) Mrs. C. Crosby, Diss. (River Waveney.) Mr. C. Davies, Haiesworth. (Easton Broad.) M r . J. Docwra, Westleton. (Dunwich River.) M r . T . Forrest, Coypu Control, Saxmundham. Mr. A. C. Gatehouse, Twickenham. (Thorpeness Meare.) Mr. W . George, Aldeburgh. (River Blythe.) Major Faine Grahame, Lamarsh. (River Stour.) M r . G . St. John Hollis, Ipswich. (River Deben.) M r . and M r s . S. Holyfield, Orford. (Sudborne Marshes.) M r . L . Howard, Woodbridge. (River Deben.) M r . and M r s . Longe, Haiesworth. (Upper Blythe.) M r . and M r s . Macdowell, Holbrook. (Holbrook Creek.) Mrs. B. H . M a n n , Campsea Ashe. (River Deben.) Mr. C. S. Mead, Ministry of Agriculture, Bury St. E d m u n d s . M r . D . R. Moore, Lowestoft. (Benacre, Covehithe and Easton Broads.) Mrs. J. Oglethorpe, Orford. (Butley River.) Mrs. A. M . Orr, Redgrave. (Redgrave Lake.) M r . R. J. Partridge, Orford. (R.S.P.B. Havergate.) Mrs. Payne, S u d b u r y . (River Stour.) Mr. A. G . Powell, Chelsworth. (River Brett.) Miss E. Roberts, D e d h a m . (River Stour.) Miss J. L . Robinson, Boxford. (River Box.) M r . J. Rolfe, T h e t f o r d . (River Waveney.) M r . F. W . Simpson, Ipswich. (River Deben.) M r . J. Southgate, Westleton. (Dunwich River.) Mrs. N . Walrond, Bury St. E d m u n d s . Dr. R. Mayor-White, Baylham. (River Gipping.) M r . L . F . Wright, Kessingland. (Kessingland Level.)
I would also like to thank Mr. Peter Nicholson, who is now the Deputy Regional Officer in the East Midlands for the Nature Conservancy, and the Earl of Cranbrook for their help and encouragement. The work was kindly sponsored by the Nature Conservancy, the Suffolk Trust for Nature Conservation and the Suffolk Naturalist's Society.
References Erlings, S. (1968).
Territorality of the Otter, Lutra lutra, L. Oikos 19, 81.
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TABLE I. Evidence for the presence of Otters in Suflfolk, obtained by field survey of tbirty 10 km. O.S. squares between Ist May, 1969, and Ist September, 1972. O.S.
Map
IO km.
Square TM TM TM TM TM TM TM TM TM TM TM TM TM TM TM TM TM TM TM TM TL TL TL TL TL TL TL TL TL TL
03 07 13 15 17 24 25 33 34 35 36 37 44 45 46 47 49 57 58 59 68 77 78 83 84 88 93 94 97 98
TOTAL
Record Cards Received
Other Positive Evidence
Sightings
4 1 6 2 1 5 2 1 64 7 1 1 20 9 3 40 1 1 1 16 1 3 2 1 1 2 1 1 1 1 200
Probable Evidence
None
2
2 1 5 2 1 3
2 1
Manjhours in the Field
2 27 2 1 2 2 12
1 1
1 35 5 1 1 19
2
6 28 1 1 1 15 1 3
1 2 1
1 2 1 1 1 1 12
56
4
128
5 3 13-5 2 1 17-5 3 1 45 4 1 2 25 7 3 30 1 1 1 10 1 2 5 2 1 5 1 1 2 1 197
TABLE 2.
An estimate of the total Otter population in Suffolk. Area 0) (2) (3) (4) (51 (6) (7)
River Stour River Gipping/ Orwell River D e b e n River Alde/Ore T h o r p e n e s s Meare Minsmere Walberswick Marshes
Area
Otters
River Blythe Easton, Covehithe, Benacre Broads and Kessingland Level (10) River Waveney (11) Little Ouse (12) River Lark
3
Otters 4 0 3 4 2 2 0
(8) (9)
3 10 5 0
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TABLE 3.
1. (2) (7) (12)
Extinct
2.
Gipping / Orwell Walberswick Marshes River Lark
(1) (5) (8) (10)
Endangered Stour Thorpeness Meare River Blythe River Waveney
3. (3) (4) (6) (9) (11)
Viable
River D e b e n Alde/Ore Minsmere Easton, Covehithe and Benacre Broads Little Ouse
Rodney B. West, 5 Dales View, Washbrook, Ipswich.