Transcript Superviviencia libre en Castilla (1753 kB.)

SURVIVAL OF RADIOTRACKED IBERIAN HARES (Lepus
granatensis) IN THE CASTILIAN PLAIN.
BARTOLOMÉ, D.J.; PÉREZ, J.A.; DÍEZ, C.; OLMEDO, J.A.; ALONSO, M.E.
Dpt. Animal Production II, Faculty of Veterinary of Leon. 24071. Spain.
E.mail: [email protected]
XXVI INTERNATIONAL IUGB (International Union of Game Biologists) BRAGA, PORTUGAL
INTRODUCTION AND OBJECTIVES.
Iberian hare is one of the most desired cynegetic species by hunters. Due to its
excellent adaptability, its area of distribution is very large, which extends through all
the Iberian Peninsula to the south of the river Ebro.
It is paradoxical that an animal with so much tradition and importance in the
cynegetic Spanish activities has not been the target of a larger number of field studies
in our country. In view of the exigency of administration of the cynegetic resources,
through the Plans of Cynegetic Organization, it is urgent the realization of studies of
populations and species-environment relation, over Iberian hares.
Such an urgency is bigger in the case of Iberian hare (Lepus granatensis), which,
without a doubt, is the least studied species within the Spanish small game.
The main objective of this work was to evaluate the survival of autochthonous
Iberian hares in a natural environment that they know perfectly, and to determine the
most frequent causes of mortality of the Iberian hares in the Castilian plain.
RESULTS AND DISCUSSION.
Taking into account the marked hares as a whole, we find that the value of the
median survival rate was 124 days, independently of any other variable. The maximum
survival rates were 376 days corresponding to an adult male. 10% of radiotracked Iberian
hares lived more than 250 days.
If we do the separation of the marked animals by sex, the median values obtained were
131 days for males and 116 days for females. With regard to survival evolution of radio
tracked hares released, we observed that females had more capacity of survival than males
during the days following the release (Graphic 1). None of the females was able to live 245
days after their release.
100
Males
Females
90
1.STUDY AREA. The realization of the study was carried out in the farm Coto
Bajo of Matallana, property of the Most Excellent Country Council of Valladolid,
located in the district of Villalba de los Alcores, in the North extreme of the province of
Valladolid (41º 53’ 45”-41º 55’ 15” N latitude and 4º 51’ 10”-4º 52’ 50” W longitude),
with a total extension of approximately 308 has. where a cynegetic fence has been built
around. The farm lacks cynegetic exploitation. Therefore, the density of the different
species is only conditioned by the relation predator-prey.
With regard to permanent vegetation, it must be highlighted the important amount
of reforested plants that includes several species such as pines, brushes and clump of
brambles. As regards farming, they stand out lands of cereal, concretely barley and
alfalfa.
2. ANIMALS. With regard to the animals, a total of 22 hares were captured, all of
them in the farm, therefore autochthonous. Among all the 22 animals, only 19 were
used for the present study, the other 3 were cast off due to several causes.
As regards the age of the hares, 9 sub-adults animals and 10 adult ones were used.
The sex proportion was 9 females and 10 males.
All the captures were done at night. Each hare was localized with the help of a jeep
and a hand spotlight. Later, the animal was guided to the place where a net of nylon
had been placed the afternoon before. Once there, the animal was captured and the
corresponding radio-transmitter was fixed as a collar to its neck.
After being determined the sex and approximate age of the animal, and after
identifying it by means of a numbered metallic crotal placed in one of its ears, the
animal was immediately liberated.
Finally, a weekly and individualized study of the animals was realized by means of
the radio-tracking system, already used with hares by others authors such as RICCI in
1983; RODRIGUEZ et al. in 1997 and ANGELICI et al. in 1999.
Each localization stopped at the moment of detecting clear activity. Finally, each
member had its own file card where it was noted in a map of the farm (scale 1:10.000)
the localization of the animal.
In the case of finding a dead hare, it was taken a photograph and the body was
taken in order to determine the cause of its death by means of a necropsy.
90
80
70
% animals alive
MATERIAL AND METHODS.
% animals alive
80
Adults
Youngs
100
70
60
60
50
50
40
40
30
30
20
20
10
10
Survival days after release
0
1
Survival days after release
0
10 19 28 37 46 55 64 73 82 91 100 109 118 127 136 145 154 163 172 181 190 199 208 217 226 235 244
1
11
21
31
41
51
61
71
81
91 101 111 121 131 141 151 161 171 181 191 201 211 221 231 241 251
Graphic 1. Evolution rates of survival of radio controlled iberian hares by sex and age.
If we do the separation of the marked animals by age, the median values obtained were
121 days for the sub-adult ones and 127 for the adult ones.
In the same way, if we study the influence of sex and age altogether, over the median
values of the survival rates, we obtain that the median survival rate of sub-adult males was
100 days, while for adult males that value raises to 162 days. In the case of females, we
obtain a median survival rate of 142 days for the sub-adult hares, while for the adult ones
the value was reduced to 84 days (Graphic 2).
Sub-adult females
Adult females
Sub-adult males
Adult males
0
50
100
150
200
Days of survival
Graphic 2. Survival rates of radiotracked iberian hares.
In the statistic treatment of the data, we did not find significant differences due to sex
nor age of the marked animals.
With regard to causes of death, of the total of drops registered (Graphic 3), we assigned
32% to predation by carnivorous, fox mainly and sheepdog (Photo 4); 21% to doubtful
causes of death; 16% to several diseases (Photo 1): European brown hare syndrome,
pseudotuberculosis, etc.; 16% due to defect in the design of the necklace radio transmitter
(Photo 3), and finally 15% to road traffic accident (Photo 2).
3. DATA PROCESSING. To carry out the statistical study was used the computer
program of statistical SPSs© (version 10.0) for WINDOWS©.
Necklace radio
transmitter
defects
16%
Road traffic
accident
15%
Diseases
16%
Carnivorous
predation
32%
Doubtful
21%
Graphic 3. Causes of death to radio-tracked iberian hares.
Photo 1. Death by
disease.
Photo 2. Death by road
traffic accident.
BIBLIOGRAPHY.
ANGELICI, F.M; RIGA, F.; BOITANI, L.; LUISELLI, L. (1999). Use of dens by
radiotracked brown hares Lepus europaeus. Behavioural Processes, 47: 205-209.
BROEKHUIZEN, S.; MAASKAMP, F. (1982). Movements, home range and clustering
in the European hare Lepus europaeus in the Netherlands. Z. Saugetierkunde, 47: 2232. (2001). RICCI, J.C. (1983). Study of released hares (Lepus europaeus) by radiotelemetry: mortality, dispersion and space use. Acta ecol., 4: 31-46. RODRÍGUEZ, M.;
PALACIOS, J.; MARTÍN, J. A. (1997). La liebre. Ediciones Mundiprensa. Barcelona.
160 pp.
Photo 3. Death by defect in the design of
the necklace radiotransmitter.
Photo 4. Death by fox predation.