Mammals in MZNA-VERT: project Human impacts in rivers of Navarra

Study Extent

The Erro River Basin is located in the north of Navarra in the western side of the Pyrenees. Its climate conditions suffer a strong change between the source of the river influenced by the Pyreneans’ climate to the mouth of the Erro where the climate becomes more Mediterranean. From north to south rainfall decreases in contrast to the temperature which increases as it reaches south. Erro Basin is characterized by a wide range of landscapes which has a positive effect on the flora and fauna diversity. The headwater’s area and the middle section of the basin are dominated by oaks and beech forests, pastures and forestry exploitation mostly consisting on pines. The last section is dominated by crops and cattle grazing fields (Rivas 1987).

Sampling

Fifteen sites were sampled from 2001 to 2003, doing at least two sampling each season in every site. Sherman traps (7,5x9x23 cm) baited with bread and oil were used. Each sampling event consisted on two nights and the total sampling effort made was 160 traps per night. Specimens were sexed and identified in field when possible. Some of the specimens captured were transported to the laboratory for further studies. In addition eleven sites were sampled using pitfall traps in order to get a better knowledge of the small mammals’ community due to the bias of using only one type of sampling method. Each sampling site was composed of six cylindrical jars (11,5 cm diameter and 13,5 cm depth) which were active from May to November 2001. Barn owl pellets, information about footprints and other mammal trails were collected during the sampling period.

Quality Control

All specimens collected from the field are deposited in the Museum of Zoology of the University of Navarra (MZNA, Pamplona, Spain) in the ‘Colección de Actuaciones humanas en el río Erro’. All the species were sexed and identified in field (when possible) and the taxonomic identity of each specimen brought to the laboratory was verified by David Galicia using suitable literature (Gosálbez 1987, Niethammer and Krapp 1978, 1982, 1990). Scientific names were validated according to Mammal Species of the World (Wilson and Reeder 2005, Palomo et al. 2007). Unique collections’ accession numbers were assigned to each specimen.

Method steps

1. All captured specimens where sexed and identified in field. Most of the specimens captured the first year were selected for further studies in laboratory. Specimens which identification was in doubt were also taken to the laboratory. Specimens brought to the laboratory were euthanized and frozen at -20ºC. Then, they were measured (tail length, body length, ear length, hind foot length, fore foot length) and weighted (body weight and eviscerated weight). After that, some specimens were selected and processed for a deeper study. Skin was removed and preserved dried. Skull, mandibles and some skeleton parts (scapula bones) were obtained and placed in plastic bags. Information of each record was systematically incorporated to MZNA database (Zootron v4.5, Ariño 1991).

Specimens were first identified to genus or species level in field using external morphology. Specimens in doubt were transported to the laboratory where their taxonomic identity was verified using suitable literature (Gosálbez 1987). Some specimens captured in field were selected for deeper studies so they were transported and processed in the laboratory. The collection is composed of 3 orders (Carnivora, Rodentia and Soricomorpha), 6 families and 18 species although the order Carnivora is represented by only 3 records of Mustela nivalis. Muridae is the most abundant family being approximately the 79% of the entire collection followed by Soricidae representing the 12 %. Most of the specimens brought to the laboratory belonged to the species A.sylvaticus and M. spretus.

1. Animalia
   rank: kingdom
2. Chordata
   rank: phylum
3. Mammalia
   rank: class
4. Carnivora
   rank: order
5. Rodentia
   rank: order
6. Soricomorpha
   rank: order
7. Cricetidae
   rank: family
8. Gliridae
   rank: family
9. Muridae
   rank: family
10. Mustelidae
    rank: family
11. Soricidae
    rank: family
12. Talpidae
    rank: family
13. Apodemus
    rank: genus
14. Crocidura
    rank: genus
15. Eliomys
    rank: genus
16. Microtus
    rank: genus
17. Mus
    rank: genus
18. Mustela
    rank: genus
19. Myodes
    rank: genus
20. Neomys
    rank: genus
21. Rattus
    rank: genus
22. Sorex
    rank: genus
23. Suncus
    rank: genus
24. Talpa
    rank: genus
25. Apodemus flavicollis
    rank: species
26. Apodemus sylvaticus
    rank: species
27. Crocidura russula
    rank: species
28. Eliomys quercinus
    rank: species
29. Microtus agrestis
    rank: species
30. Microtus duodecimcostatus
    rank: species
31. Microtus gerbei
    rank: species
32. Microtus lusitanicus
    rank: species
33. Mus domesticus
    rank: species
34. Mus spretus
    rank: species
35. Mustela nivalis
    rank: species
36. Myodes glareolus
    rank: species
37. Neomys fodiens
    rank: species
38. Rattus norvegicus
    rank: species
39. Sorex coronatus
    rank: species
40. Sorex minutus
    rank: species
41. Suncus etruscus
    rank: species
42. Talpa europaea
    rank: species

The collection is mainly formed by specimens from Erro Basin but there are also records from other localities nearby the basin.