Feeding habits of the Eurasian otters (Lutra lutra, Linnaeus, 1758) living in Putna Vrancea Natural Park

Feeding habits of the Eurasian otters (Lutra lutra, Linnaeus, 1758) living in Putna Vrancea Natural Park

PhD Student: George BOUROȘPhD Student: George BOUROȘ

Biologist: Rocío HERMOSILLA GARZÓNBiologist: Rocío HERMOSILLA GARZÓN

Biologist: Jesús Alberto SÁNCHEZ PARDO Biologist: Jesús Alberto SÁNCHEZ PARDO

Introduction

© © Nicole DuplaixNicole Duplaix

Eurasian otter is a semi-aquatic carnivore belonging to the Mustelidae family.

Otter is classified as Near Threatened by the IUCN and considered Vulnerable by the Romanian Vertebrate Red Book;

Otter is one of only a few European carnivores that has developed the ability to actively forage both in water and on land;

Having knowledge of what individuals eat is one of the most important aspects of otter ecology, it is a strong relationship between the availability of food resources, the distribution and survival of the species.

Aim of this study is to determine the feeding habits and the trophic resources, on which depends the survival of the otter species from Putna Vrancea Natural Park and Carpathian Mountains.

Fig. 1 Euroasian Otter (Lutra lutra)Fig. 1 Euroasian Otter (Lutra lutra)

Materials & Methods

The annual average flow of the river Putna at hydrometric station Lepșa, is 1,83 m3/s and in Tulnici is 4,58 m3 /s;

Riparian woods consist mainly of alder (Alnus glutinosa, Alnus incana) and willow (Salix spp.).

Study was conducted on the rivers and streams belonging to 8 basins from Putna Vrancea Natural Park;

The park is located in SE Romania, NE of Vrancea County and covers an area of 382.13 km², with altitude ranging from 435 m in the valley of the Putna River to over 1785 m in Goru Peak.

Putna River collects all the streams in the park and forms a narrow west - east oriented valley. Most of the flow takes place at the end of the spring (44%) and early summer (30%)Fig. 2 Study area: Putna Vrancea Natural Park in RomaniaFig. 2 Study area: Putna Vrancea Natural Park in Romania

Materials & Methods56 otter spraints were collected from December

2012 to September 2013 from 36 different sites;For any spraint were noted following

information: date, time, observer, geographic coordinates, river or stream name, site code and estimated spraint age;

Spraints were collected in two different periods of the year, in order to notice variations in the trophic resource utilization by season;

Fig. 3 Sampling sites (left)

Fig. 3 Sampling sites (left)

Fig. 4 Collecting otter spraints (right)

Fig. 4 Collecting otter spraints (right)

Materials & MethodsSpraints were individually soaked in a metal

container with 1/3 of water and 2/3 of detergent for 1-3 days to a week;

Samples were washed by tipping the contents of the cup into a 0.5 mm fine mesh sieve;

The spraint particles were then carefully removed from the sieve and placed in a white plastic tray;

Using different size forceps and needles, any bone fragments were identified, picked out and sorted into groups.

The largest vertebra and exoskeletons could be identified with the naked eye, but for the smallest was used a magnifier and a microscope (10 X).

The percentage of occurrence of each species was plotted per spraint and secondly the frequency of occurrence per prey item was also calculated as:

RFO % = Number of occurrences of a prey group RFO % = Number of occurrences of a prey group x100/Sum of occurrences of all prey groupsx100/Sum of occurrences of all prey groups

After being analysed, spraints were dried and stored in a collection, in plastic tubes which has been assigned a code and date;

Fig. 5 Spraints prepared for the analyseFig. 5 Spraints prepared for the analyse

Fig. 6 Spraints particles identifyingFig. 6 Spraints particles identifying

Results & DiscussionRelative frequency of occurrence in spraints of various classes of prey species (RFO%)

From a total of 56 spraints, 53 of them contained the remains of fish;

RFO% results: 31% fish, 24% amphibians, 21% insects 16% mammals, 3% snails , 3% plants and 2% reptiles.

31 % of all appearances was the fish;Plundering of amphibian breeding sites during

oviposition in spring;Reptiles and gastropods low occurrence frequency in

the analysed spraints;

Results & DiscussionPercentage (%) of classes of prey species in total spraint analysis

57% fish, amphibians 22%, mammals 15%, insects and reptiles 3% each, gastropods 0.1% and plants 0.2%.

during winter-spring, fish consumption was reduced by 8%, as compared to the second period when it was 60%;

Amphibians 30% in winter-spring, while during summer only 16%;

Mammals 12% in winter-spring and 17% summer;Plants 0% in winter-spring, 0.4% in summer;

Results & DiscussionThe percentage (%) of occurrence of prey species classes in each of analyzed spraints

% of prey species groups % of prey species groups was calculated for each was calculated for each spraint, for both study spraint, for both study periods;periods;

some spraints were some spraints were composed 100% just from a composed 100% just from a prey class, most of the time: prey class, most of the time: Pisces, followed by Amphibia, Pisces, followed by Amphibia, Reptilia and Mamalia;Reptilia and Mamalia;

For first study period, in a For first study period, in a single spraint could be single spraint could be identified a consumption of identified a consumption of of varied prey species, unlike of varied prey species, unlike the second study period;the second study period;

Results & DiscussionThe analysis of otter feeding habits from Natural Park’s river basins

High altitude river basin samples Correlation between the altitude, river type and content of the spraint;

Amphibians :40 % in Strâmba RB and mammals in 30%, while in Ostog RB amphibians were 45 % and mammals 26 %.

Fish remains were present in a low density, 25 % in Strâmba RB and 27 % in Ostog RB;

Results & DiscussionLow altitude river basin samples

Results & Discussion

Fig. 7 Reptiles remains Fig. 7 Reptiles remains

Fig. 8 Sorex spp. & fish jaws Fig. 8 Sorex spp. & fish jaws Fig. 10 Fish remains & jaws Fig. 10 Fish remains & jaws

Fig. 9 Amphibians remainsFig. 9 Amphibians remains Fig. 11 Sorex spp. Fig. 11 Sorex spp.

Fig. 12 Mammal Fig. 12 Mammal

Conclusions

Fig. 13 Spraint on a stone in LepșaFig. 13 Spraint on a stone in Lepșa

Most of studies describe otter as piscivorous, but recent studies suggested that the otter may be better defined as an opportunistic predator;

Having knowledge of what individuals eat is one of the most important aspects of animal ecology.

The information about the otter diet is clearly important for otter conservation.

Fishes were prefered by the otters but in the lack of them, they are able to adapt to other trophic resources: amphibian, mammal, reptile, insect etc.

A difference of otter feeding habits was observed between particular habitats.

AcknowledgementsFor Support:For Support:

For advices:For advices:Prof. PhD. Dumitru MurariuProf. PhD. Dumitru MurariuPhD. Silviu ChiriacPhD. Silviu Chiriac

For training: For training:

For help during field work:For help during field work:Virginia García LópezVirginia García LópezFFrancisco rancisco PParra arra RRodriguezodriguezManuel Manuel Menéndez PuertasMenéndez PuertasRocío Hermosilla Garzón Rocío Hermosilla Garzón Jesús Alberto Sánchez PardoJesús Alberto Sánchez Pardo

For publicity : For publicity :

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