 |
 |
|
|
|
|||
|
|||
|
|||
|
|
|
|
|
|
|||
|
|||
|
|||
|
Gera Pál Summary of Hungarian Otter Surveys (Lutra lutra), 1995-2001. |
Az elektronikus változat alapja:
Gera Pál
Summary of Hungarian Otter Surveys (Lutra lutra), 1995-2001.
Foundation For Otters (Alapítvány a Vidrákért)
Nyírpalota utca 60. 1156 Budapest, Hungary
Translation: Dénes Nagy
2001, Gera Pál
ISBN 963 00 8142 3
Printed at 3BT, Budapest
Introduction
Nowadays, the conservation of a strictly protected, highly endangered, at some areas rare or even extinct species can not be successful, unless considerable knowledge is gathered about it. We have to discuss the information available about its area, distribution, if possible density, and also the picture formed about it by the public. The latter approach is very important, because protection strategies should (have to) be based on the attitude of those people who have any connection with the species. Attempts to reintroduce carnivorus species (e.g. wolf, lynx) were usually unsuccessful because strategy makers failed to incorporate or missed the connection of the public to the species.
Foundation For Otters (Alapítvány a Vidrákért) has managed the survey of otters in Hungary since 1995 to the present (May 2001.). As the director of this foundation I have guided this work.
During my work I have faced the problems of protection, which occurred mainly after the political changes (1989-90) followed by economical reorganisation. Privatisation brought new, previously hardly known challenges for Hungarian nature conservationists, authorities and organisations.
Besides the above work I was responsible for the otter breeding program of the Budapest Zoo, the results of which I am highly proud of, as it concerns an endangered species.
Below I would like to present a kind of abstract, summarising my findings about the ecology, etology and breeding of otters, based on my work in the Budapest Zoo, including the results of the national surveys and an evaluation of the various aspects of the "otter problem"..
Behaviour, reproduction and ecology of otter
Before examining the Hungarian distribution of the species, I would summarise the knowledge about the otter as a biological organism. I mainly refer to a former work (Gera: Ökológiai hálózat..., 2000).
Otter usually moves carefully, mainly at night. This makes it difficult to spot or observe. Its area is signed by scent marks, but at good quality habitats (e.g. fishing ponds) individual areas may overlap. It seems that enough prey and nesting place lowers the territoriality of this species. This could explain the fact (which I experienced several times) that e.g. on a fishing pond half dozen otters simultaneously occur. They may be female otter(s) with cub(s) , but density shows that more adult otters may use the same habitat without significant aggression. Nevertheless, otters from the same sex can not be held in captivity without high-level aggression, even when food and hiding place are over-insured (Gera: Szabadnak szülessenek..., 1998).
I collected the following voices of otters (Gera: Szabadnak szülessenek..., 1998):
Otters have a breeding season in some regions of its area (Northern Europe), but not in other ones (Southern and Central-Eastern Europe). Under Hungarian climate, food resources are available all round the year, so breeding and nurture may occur at any time. The lack of breeding season is probably due to the same reason in Southern and Eastern regions, but in the North changing food resources play a significant role (Gera: Szabadnak szülessenek..., 1998).
During the breeding males visit the territories of females. If a female is not impregnated, she is not be susceptible for a couple of weeks, then becomes receptive again. In the case of captive otters, females have a 30-45 days long sexual cycle with a 10-14 days long susceptible period. Besides this, little is known about the female's sexual cycle, but also about nurturing, the role of male in nurturing, the maturing time of the cubs, the changes of territory during nurturing, the migration and survival of young adult otters and their ecological needs (Gera: Szabadnak szülessenek..., 1998).
According to my data about captive otters pregnancy lasts for 60-65 days, and the female stays with cubs for 8-12 months. Female otters mature between 16-24, males 24-36 months old. Average litter size is two, cubs are blind and almost naked. Cubs open their eyes in 30-35 days, start to consume solid food in 45-40 days, and are being introduced to swim and hunt in 55-60 days. After 90-110 days otter cubs are virtually "graduated", but stay longer with the female. Mortality of cubs can reach or exceed 50% during the first 3 months (Gera: Szabadnak szülessenek..., 1998).
After the cub's eyes are opened, they come through a training which consists of accustoming to water, swimming, grooming and vocalising signs. This is the most critical period, because aquatic-life is not easy even if it is genetically predisposed. Accidents can happen, and the lack of accurate grooming can have bad effects around winter. Wet fur may causes chill and this can be disastrous.
A half-year old otter can be handled as adult, of course not in biological means, but they have all the behavioural abilities that adults have to stand their ground. They still stay with their mother, but soon they break up.
During nurturing, the female otter uses more holts, nests in her territory, for different periods of time. After giving birth , she stays in one holt for 7-10 days, but after that changes resting places every 3-5 days. After cubs can move individually these changes are more frequent. The Female keeps the nest clear, changes bedding (leaves, grass) daily. Used bedding is taken far away from the holt (Gera: Szabadnak szülessenek..., 1998).
Otter usually uses holts as resting places. Holts are normally burrowed by the otter. These holts are in water banks, under the roots of dry-rotten trees. Sometimes an otter chooses a resting or natal place in reed-bed or among waterside plants. To establish a natal holt, the female sometimes goes far from the water, and after the cubs eyes are opened at their age of 2-3 weeks, she comes back to another holt close to the water. This behaviour probably occurs mainly along rivers, where the changes of water level may explain it.
Otter signs the holts actually in use, sprainting near or (according to my experience) at the entrance places. When singing its holts, the otter often formes a ball made of grass or mud, or a heap connected by water or slime, 5-15 cm in diameter. Usually the otter spraints on it. It may be the sign of a kind of territory border, but I find them usually at or near holts. Sometimes these balls can be found where no holts are known, or under bridges, on dams.
Environmental conditions determine the location of resting places, uniform description can not be written. However, otter creates these in calm, silent areas, without the disturbance of people, dogs, foxes, and where the vegetation is dense. The frequency of holts is unknown, but one otter always has more than one. The number can be influenced by:
If more individuals occur in one place, a kind of hierarchy may form. I could not experience its system (whether it exists only between males, only between females or independent of the sex), but I find that otters adapt to each other during when they use the same place, and this defines their behaviour. Among the otters of the Budapest Zoo, where I worked as a tender between 1986 and 1999 I found that a kind of ranking was always formed in the first days. I always let the male to the place of female. My experience was that the female did not let the male near to her hole, she was the ruler. The male tolerated the bites of female and kept a low profile for 7-10 days, even if he was larger and stronger than her. After the female let him in her hole, her dominance was over. It was interesting that female and male otters always excepted each other in the water, they were playing as old friends, but after swimming the female became aggressive.
In my observation otters spraint at regularly used sprainting sites every 7-10 days. If more otters are present a kind of hierarchy may determine which otter spraints where. I have no proof for that, it's just a theory of mine. Anyway, if fresh spraints can not be found in 10 days, the area must be considered as one which otters use rhapsodically. This area may be far from the other, better places, or a more migratory, low-ranking individual uses it, or it does not ensure good ecological quality, so visited only during wandering.
The migration of wild otters is hard to follow. Although scientific methods, as tracking in snow, radioactive zinc isotope tracking from spraints or radiotelemetry are available, these are expensive, and may be influenced by the possibility of individual differences.
It is supposable that females are more site-attached than males. This can be important in nurturing. Females also have smaller territories than males. "Settled" otters occasionally leave their area, mostly the males during breeding. Migratory otters are usually young adults or subadults. An otter with a territory may leave its area because of external reasons: stronger rival, changes in the area, for example: contamination, lowering the level of a fishing pond, grubbing up the vegetation. Anyway, if the same area (e.g. fishing pond) is used by more adult otters, their hierarchy may determine the use of resources.
An interesting question is how human disturbance influences otters? Otters are flexible, readily adapt to their environment. As an animal leading hidden lifestyle it is normally not known whether it is present or not. Tracks can be spotted mainly in the winter, , without the dense vegetation, in snow. This is also the time of the year, when authorities receive more claims about economic damages caused by otters around fishing ponds. Surprisingly enough, otters can be found even in areas frequently used (disturbed by) humans, if they feel it safe. It does not happen very often, but sometimes occurs. It is also possible that these individuals are marginal ones, without a better territory. Still the question remains, why does an otter inhabit these areas?
Summarising my experiences, the needs and factors in selecting territories may be the following:
1. Food
The territory has to offer enough food resources. The otter's main diet consists of fish, but it also consumes amphibians, crabs, shells, small mammals and birds. Still, fish is the most important prey (Lanszki: Egy biotópban élő..., 1993).
I judge the most frequent prey size is around 200-300g. The bigger the prey, the harder it is to handle. However, sometimes otters attack larger fish, but they usually can not catch, but just harm it, though in some cases such hunt may be successful. Slaughter is typical for subadults, rarer among adults, but may occur. Otters can cause significant damage mainly at so-called "wintering ponds".
2. Contamination, water quality
Contaminated waters (pesticides, industrial pollution) represents one of the most significant problems in nature/environment conservation. The water body itself becomes contaminated on the one hand, and the food chain on the other, both affecting otter population through bioaccumulation, causing health depletion (e.g. infertility) or even death. Various pollutants have already destroyed whole biological systems, and may happen in the future again (e.g. cyanide and heavy metal spill at Tisza and Szamos river). Impacts of contamination are perceptible for decades. Otters are quite vulnerable, because they have a long potential lifespan, low reproduction rate, and are situated at the top of the food chain (Gera: A vidra védelme..., 1995; Gera: Vidravédelem..., 1999).
3. Habitat complexity
Beyond food, otters' habitat must offer aquatic and bankside vegetation, holts and caves to ensure hiding places. The role of bankside vegetation is especially significant. Without vegetation or with highly disturbed or thinning vegetation otters rarely stay, or use the area as corridor (Alapítvány a Vidrákért: Jelentés..., 1995; Gera: Gondolatok..., 1996).
Otter breeding was successful in the Budapest Zoo for several times (Gera: Szabadnak szülessenek..., 1998). All together 10 cubs were born between 1993 and 1999. Several of them were taken to European zoos or zoological parks. This was the contribution of the Budapest Zoo to the captive breeding project in the otter conservation program coordinated by Association of European Zoos.
I made regular notes on the behaviour of each otters. In this way I collected interesting data about nurturing the cubs (as mentioned before), but also about the behaviour of females during pregnancy and parturition. I hope these data can contribute to a successful future captive breeding program (Gera: A vidra..., 1994; Gera: Szabadnak szülessenek..., 1998).
Below I try to outline the notes collected during the captive breeding in Budapest Zoo.
Breeding season can occur at any time of year. Pairs are mating for 7-10 days. Copulations, as usual at Mustelids, are violent, forceful. The shortest copulation took 12 minutes, the longest 21 minutes.
Copulation took place mainly in the water. Pairs changed during playing. The number of copulations onshore is less, but I saw it myself at the zoo.
Conceived females show the following somatic and behavioural changes during the last 4-14 days:
Experience of the Hungarian surveys
Until now, the Foundation For Otters organised national surveys twice (1995-96, 1998-99). In January 2000, after the contamination spill at Tisza and Szamos river we initiated a local research, and in 2001, some areas were investigated within the National Biodiversity Monitoring Program. These data are continuously integrated with other, constantly incoming reports and data. The methods of surveys, distribution maps and the questionnaire of surveys can be found in the Appendix.
Now ,before we ask the question where, in what kind of habitats otters live, we must clarify some terms.
During our work, the occurrence of otters was considered regular, when we found fresh spraints during the biweekly or monthly surveys . Freshness was concluded from the consistence of spraint.
The occurrence was considered sporadic, if we could not find any fresh, but older spraints during the survey period.
We considered otter absent in areas, where we could not find any spraints or signs during the survey period.
These categories are not used in the standard methodology of surveys, but we had to systematize the results. The categories were deducted from my subjective experiences and field observations. I hope that this evaluation system matches the scientific methods, although was designed mainly for practical reasons.
Summarising the above, wetlands with regular otter presence (natural and artificial ponds, sections of rivers, rivulets and canals, reservoirs) have the following characteristics:
Where is the occurrence of otters sporadic?
Where are otters absent?
Factors of otter migration
In Hungary, the unequal distribution of otters may cause different problems for preservation from region to region, because of the following variables:
It is clear that the characteristics of the otter population in Somogy county with an abundance of fishing ponds and those of a mountainous area without many wetlands are markedly different. However, we ought to know:
During the surveys we collected the following data:
In order to be in contact, otters of different regions must be able to get from one place to another. As creature of wetlands, otters frequently use corridors based on waterways, especially those with the following abilities:
During wandering otters are facing the following difficulties:
Otters and people
During our surveys we took time to collect the opinion of locals about the otter. We had the chance to do this when we met them face-to-face. First, we were interested in their knowledge about otter as a species, second, in how they judge otter preservation, third, if they claimed that preservation was inadequate what kind of solution would they accept? We asked these questions at those surveying sites where otter presence was regular (mainly at fishing ponds, reservoirs, rivers planted with fish).
In 1995-96, at the first survey (between October and March) we registered the following answers:
At sites with "otter problems" locals mentioned live-capturing, relocating and financial compensation by the state as possible solutions.
In 1998-99, at the second survey (between October and March) we registered the following answers from locals:
We collected the most opinion of locals about otters during the surveys in 2000-2001. The bulk of them (around 90 percent) came from Tisza and Szamos region. Other interviewees live along Bodrog, Szigetköz, Dráva and Duna.
Answers of locals elsewhere than the Tisza and Szamos region were as follows (between 2000 October and 2001 April, to the same questions):
Already during the first survey (1995-96) illegal hunting of otter seemed to be significant problem. At the first, we thought it originated in the conflict between nature preservation and economic needs, such as the lack of coordination of compensation for damages caused by protected animals. We concluded that although it may be true, but persecution and damages caused by otters are not directly connected.
Persecution was experienced at some waters where economic damages were not considered significant, but was not at others where damages were considered intolerable. What is the explanation?
Beyond illegal hunting, wetland management could be problem for otter preservation. Appropriate wetland management should not use the following techniques:
Management methods are directed by laws, state funds, and last but not least the acceptance of the economic activity in question. Awareness-raising campaigns for extensive management don't deliver, unless the idea is supported by law, economic incentives and subsidies. Owners of fishing ponds will use environmentally sustainable methods if they benefit from water tax lowering, tax or credit facilitation, etc.
Thus the most important aim is to converge nature preservation and agriculture. The values of these areas are different now, but this has to change soon. On the one hand, this is a political question, because governmental agriculture policy defines the possibilities. On the other, hand this is a question of attitudes: what involved individuals accept from sustainable agriculture and economy.
Methods of this sustainable policy should be incorporated in the official economical system by economists. Everybody should clearly see the benefits of the sustainable management e.g. at a fishing pond both for the owner and the community (country) on the long run. After these steps, campaigns can begin to raise the attention of owners and managers.
Otter is involved in these processes, because in Hungary lots of individuals of this species can be found at private fishing ponds and wintering ponds. It is a fact that otters can cause significant damages, but owners tend to overestimate it. Compensation, as one of the most preferable demand, is not supported by state, although the need for it is well-known (Gera: Egy hosszú távú..., 1998). Legalising of otter hunting is also rejected, because Hungary has one of the strongest otter populations in Europe, which has great value. Preserving otter is one of the most important tasks of wetland protection. As a top level predator, it may indicate the general health of wetlands, so any conservation steps may help us to preserve wetlands.
In order to help this preservation work financial damages caused by otters have to be measured properly. Some years ago I suggested a methodology for this (Gera: A vidravédelem..., 1998), so we have a basic tool to judge compensation claims. This suggestion was accepted by both government agencies of nature preservation (Management of Nature Parks) and agrarian professional associations (Hungarian Association of Fishermen, Hungarian Association of Anglers). Hereby I introduce the main principles of this methodology:
An appropriate evaluation according to the above aspects may justify compensation demands (or establish their overestimation), and establish an official recommendation for solution. However, we should strive for minimizing such cases. The best way to achieve this is to create an understanding between nature conservationists and managers, orienting both parties towards the same aim (by tax, credit or other state reliefs).
Summary and recommendations
Based on the foundation's otter protection work carried out since 1995, we can confidently say that the Hungarian otter population is stable and developing. Even the expansion of populations may be observed in domestic wetland areas.
The ecological accident along the Tisza and Szamos rivers in 2000 did not cause perceptible damages to the local otter population. However, the long-term effects of heavy metal contamination may only be established in years.
The most apparent expansion of the otter population takes place in the Hanság and Szigetköz regions, while the situation is the worst in Pest county, due to its dense road network and theintensive human disturbance, pollution and transformation of wetlands (e.g. concrete river beds). In spite of this, there are particularly good "otter places" even here: increasing their number should be a goal for the future.
In Hungary, several factors may limit the protection and future population increase of the otter:
In my opinion, the above problems could be solved by the following instruments:
Ackowledgements
Hereby I would like to thank for the help of all those who supported the Foundation and myself with their efforts. I'm honoured by the will to help the protection of otters, and it is not a commonplace that it means really much to me and to all those who are part of the Foundation's work.
I thank the ELTE Nature Conservation Club for establishing the Foundation and making it possible for me to coordinate it. I also thank the Ashoka Foundation for their internship which enabled me to devote most of our time to otter protection. I thank the Budapest Zoo for effectively supporting my work. And last but not least I thank the Nature Conservation Office of the Ministry of Environment for their trust to contract me and the Foundation with the task of mapping the distribution of otters in Hungary.
Here I could list all those who actively supported us with their work, but I don't, since I wouldn't like to skip anyone, and even with the biggest care, mistakes may be made. But I am also aware that without them neither my work nor that of the Foundation's would not be where it is now, thus this study could not be written. I cannot express in words or write down how grateful I am towards all of our supporters, thus I could only ask them to accept this simple, still all-encompassing word: thank you.
Appendices
Appendix I.
Methods of surveys
During the surveys we used the IUCN's "minimum-standard" method to carry out the work.
In essence it means that at least a 600 m long, representative stretch must be closely examined in each area. In practice, e.g. on a riverside at least this distance must be looked at, and only after examining the whole stretch, can the presence or absence of the otter established. In case there is an otter sign in the first 10 metres, the survey does not need to be continued, the area in question may be considered otter-inhabited. The same goes for other examination points. Priority points to be looked at: waterways under bridges, dikes between lakes, reservoirs, river mouths.
Appendix II.
Survey form
1. County
1.1. Closest settlements
1.2. Name of the observation area
1.3. Size of the area (estimation), proportion of water surface.
1.4. Description of the area:
artificial pond, natural lake, river, channel, reservoir, other.
1.5. Type of waterbank vegetation: reed bed, meadow, forest , other.
2. Results of the survey: otter presence - absence
2.1. Is the otter presence continuous in the area: yes - no
2.2. Method of observation: footprint, spraint, prey remnants, other
2.3. Weather conditions during the survey: rainy, snowy, sunny, other.
2.4. Circumstances of observation:
walking, from an observation point, on a dike, on the bank, under a bridge etc.
3. Any other relevant information.
Appendix III.
Survey form for otter monitoring after the cyanide and heavy metal pollution on the Tisza and Szamos rivers
1. County
1.1. Closest settlements
1.2. Name of the observation area
1.3. Size of the area (estimation), proportion of water surface.
1.4. Description of the area:
artificial pond, natural lake, river, channel, reservoir, other.
1.5. Type of waterbank vegetation: reed bed, meadow, forest , other.
2. Results of the survey: otter presence - absence
2.1. Is the otter presence continuous in the area: yes - no
2.2. Did otters live in the area prior to the pollution?
2.3. Method of observation: footprint, spraint, prey remnants, other
2.4. Weather conditions during the survey: rainy, snowy, sunny, other.
2.5. Circumstances of observation:
walking, from an observation point, on a dike, on the bank, under a bridge etc.
2.6. What do the local people say about otters?
3. Any other relevant information.
Appendix IV.
Maps: 1995-96 survey; 1998-99 survey; MBmR Program; post-cyanide spill
Literature used
Foundation for Otters (1996) Jelentés a fokozottan védett és veszlélyeztetett vidra országos állományfelméréséről.
Foundation for Otters (1998) Jelentés a fokozottan védett és veszélyeztetett vidra országos állományfelméréséről.
Foundation for Otters (2000) Gyorsjelentés a Szamos és Tisza folyót ért ciánmérgezés utáni vidrakutatásról.
Foundation for Otters (2001) Kutatási jelentés az NBmR program keretében végzett európai vidra állományának felméréséről.
Foundation for Otters (1998) Javaslat a vidra okozta halgazdasági károk felmérésének módszertanára
Gera, P (2000) Ökológiai hálózat és vidravédelem, vitaanyag, 1-24. Foundation for Otters.
Gera, P (1998) Szabadnak szülessenek, szabadon élhessenek. 1-82. Foundation for Otters.
Gera, P (1995) A vidra védelme halastavakon és a vizes élőhelyeken. 1-16. Foundation for Otters.
Gera, P (1999) Vidravédelem - Egy hosszútávú stratégia alapelvei hazánkban. 1-20. Foundation for Otters
Gera, P (1994) A vidra zárttéri viselkedése és szaporítása. Állattani közlemények, 80.: 65-70.
Gera, (1996) Gondolatok és ajánlások a vidra jövőbeni védelméhez. Foundation for Otters
Lanszki, J (1993) Egy biotópban élő menyétfélék táplálék összetételének vizsgálata (a fonói halastó körzetében). Diplomadolgozat
Contact persons: