Volume 3 Pages 1 - 51 (March 1988)

Citation: Braun, A.-J. (1988) The Otter (Lutra lutra) in Brittany.  IUCN Otter Spec. Group Bull. 3: 5 - 8

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The Otter (Lutra lutra) in Brittany

Alain-Jacques Braun

Étude Loutre, 56370 Le Tour du Parc, Le Mare, Brittany, France

Brittany (NW France) is a massive, low-lying peninsula with a highest altitude of only 390m. The drainage system is dense but rlvers are usually short, few exceeding 100 km in length. The climate is oceanic, mild and with moderate rainfall. Brittany covers 34.077 sq km with a population of 3,530,000 (104/km2).

Until the mid 1950s the otter was common and locally abundant throughout the province and exploited all available habitats fron small oligotrophic streams (less than 2m wide) and large eutrophic rivers to wetlands, sea coasts and islands. Regarded as a pest, it was intensively trapped and hunted, frequently with packs of hounds in the British manner but in a less organised way. Tallies for otter hunts ranged from 5 to over 60 animals per year during the period 1930-1970. Poisoning with strychnine also occurred in the Loire area, in the south, but with negligible results. It has been estimated (Braun, 1986) that during the period 1930-1970, between 16,000 and 40,000 otters were destroyed or captured.

A decline was first noted by otter hunters and trappers during the 1950s and early 60s. We cannot say if it coincided with the appearance of pesticides or not (see Chanin & Jefferies, 1978). Very few fish have been analysed recently for pesticides and heavy metals (only 49 samples). One sample from the Ille at Vilaine departement contained 0.595 mg/kg fresh weight, which is higher than the maximum level of 0,5 mg/kg set by the National Academy of Sciences (USA). Mercury was found in fish from several rivers in all the departemants of Brittany.

While industry in Brittany has remained on a small scale, slaughter houses , canning factories, fish farming and poultry units have grown tremendously and have generated locally high levels of pollution. Many streams are in a state of neglect, obstructed by dead vegetation and which results in low biological productivity. Some streams are being reconstituted by conservation groups. However, at present, the general situation of rivers is relatively good, especially by comparison with other regions, e.g. the north and east, of France.

The present distribution of Lutra lutra is not accurately known because of a lack of specialists and due to differing and uncoordinated survey methods. According to our own information (from field surveys and informants), the species has disappeared from most of the islands and sea coast but is still found inland, especially in headwaters in the central part o£ the region. In the southern regions of Morbihan and Loire Atlantique otter populations live in coastal marshes and sometimes use the sea shore and estuaries. Breeding occurs regularly in 4 departements - Finisterre, Cotes du Nord, Morbihan and Loire Atlantique. In Ille et Vilaine breeding seems to be very irregular. The largest and most healthy population appears to live in Morbihan. Records collected since 1970 show that the mean number of young per litter in Brittany is 3.2 (n = 13) (Braun, 1986 and unpublished).

Between 1970 and 1987 causes of otter mortality in Brittany were recorded (Braun, 1986 and unpublished). The results are given in the table below.

Table 1: Causes of Otter Mortality in Brittany

The figures for traffic accidents appear very high compared to other European regions - c.f., for example, 18% in Czechoslovakia (Barus and Zejda, 1981) or 10.6% in the German Democratic Republic (Stubbe, 1980). Could this be due to a higher density of otters in our region? In 22 cases (73.3%), the otter was killed on a road/bridge crossing a wetland or separating two wetlands. In 25 cases (83.3%) the accidents occurred in areas where the species is considered as breeding regularly.

Trapping to control "pest species" such as muskrat (Ondatra zibethicus), coypu (Myocastor coypu) and mink (Mustela vison) is widely practised. Since the last 10 years the American mink has colonized most of the suitable habitats in 3 departements -Morbihan. Finistere and Cotes du Nord. Locally the species is abundant and this has led to an increase in trapping. The use of gin traps, even when these are modified (a law requires the teeth to be filed off or covered with plastic or rubber) is still a threat to otters as well as to the highly endangered European mink (Mustela lutreola) which survives in very low numbers in Brittany. Evidence of Mustela vison was found in over 65% of the sites used by otters in Morbihan. Proposals made by the author in 1983 to use cage traps in areas frequented by Lutra lutra and Mustela lutreola were approved by the Morbihan Hunters Federation in 1987. It is hoped that this will soon be extended to other departments.

All recorded otter deaths by drowning occurred in southern Brittany (Morbihan and Loire Atlantique) where eel nets are commonly set. Braun (1983) recommended the use of excluders on fyke nets but no decision has been reached.

Poisonous baits (poison type unknown) were laid to get rid of muskrats over a large marsh in Morbihan, resulting in the death of an entire family. Dogs also cause problems especially during the breeding season. The 4 otters killed by dogs were estimated to be aged 3-4 months old. Castor fiber was introduced in Finistere in the 1960s and 70s. Fights between beaver and otter occurred twice, each time an otter being killed. Braun (1986) suggests that otters should not be re-introduced in areas where beaver exist.

In conclusion, while the situation of the otter in Brittany seems much better than in many other regions of France, it appears that many threats still exist. Some could be stopped or substantially reduced with the enacting of laws such as mandatory use of cage traps and excluders for fyke nets. Education and training of shooters and trappers should emphasize the conservation of Lutra lutra and Mustela lutreola and include methods for selectively trapping only target species. Traffic accidents could be reduced by installing reflectors near bridges and by modifying culverts. A study of this problem has been carried out by the author on behalf of the Regional Road Department which should lead to some conservation measures being taken in 1988. Finally, 3 otters are being analysed for organochlorlnes since we know little of the effects of pollution on our population.

Conserving the otter in Brittany is a real challenge for naturalists but unfortunately specialists are few and funding is very restricted. More studies should be made as well as a complete and well organized regional survey. Informing the public is another task which the author initiated in 1982. His slide programme has been shown to over 10,000 people all over Brittany and a large exhibit was organized at the Museum of Natural History in Nantes (10,000 visitors). The WWF-France has given financial assistance to the author but more money is needed if we are to save this fascinating species!

REFERENCES

Barus, S. and Zejda, J. (1981). The European otter (Lutra lutra) in the Czech Socialist Republic. Acta Sc. Nat. Brno. 15: 1-41.
Braun, A.-J. (1983). Repartition de Lutra lutra L. dans la zone du Lac de Grandlieu (Loire-Atlantique). Premiere phase 1981-82. Unpublished internal report to WWF-France. 15 pp.
Blanchon, J. J. and Braun, A.-J. (1983). Statut de la loutre sur la basse Vallee de la Bouzanne (Indre). Groupe Loutres Sfepm/Direction Departementale de L'Agriculture/Delegation Regionale a l'Architecture & a l'Envlrormement, Region Centre. 13 pp.
Braun, A.-J. (1984). A brief history of Lutra lutra in Brittany. Unpublished report (in English). 12 pp.
Braun; A,-J. Causes de mortalite chez Lutra lutra en Bretagne & propositions de mesures destinees a reduireles pertes: 1970-1986. Unpublished report to WWF-France. 9 pp.
Braun, A.-J. (1986). Causes of otter mortality in Brittany (1970-1985). Unpublished report to Vincent Wildlife Trust (In English). 7 pp.
Braun. A.-J. (1986). La loutre en Bretagne. Statut et repartition. Impact des amenagements, en particulier en riviere. Propositions de mesures de sauvegarde. Delegation Regionale a l'Architecturc & l'Environnement, Rennes. 45 pp.
Stubbe, M. (1980). Die Situation des Fischotters in der D.D.R. In Reuthar, C. and Festetica, A. (1900). Der Fischotter In Europa - Verbreitung, Bedrohung, Erhaltung. Selbatverlag, Oderhaus and Gottingen. pp. 179-182.

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