European Journal of Wildlife Research

, Volume 54, Issue 4, pp 571–579

Diet of the Iberian hare (Lepus granatensis) in a mountain ecosystem

Authors

  • Joana Paupério
    • CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos & Dep. de Zoologia e Antropologia da Faculdade de CiênciasUniversidade do Porto
    • CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos & Dep. de Zoologia e Antropologia da Faculdade de CiênciasUniversidade do Porto
Original Paper

DOI: 10.1007/s10344-008-0181-z

Cite this article as:
Paupério, J. & Alves, P.C. Eur J Wildl Res (2008) 54: 571. doi:10.1007/s10344-008-0181-z

Abstract

The diet of the Iberian hare (Lepus granatensis) was studied through microhistological pellet analysis in two areas from a mountain ecosystem in Central Portugal. Fecal pellets were collected monthly in 24 plots spatially distributed throughout the two study areas. For each period, a sample of 15 to 20 pellets was milled and 400 epidermal fragments were identified, by comparison with a reference collection. A wide range of plant species was observed in hare’s diet. Grasses represent the basis of the Iberian hare diet, with frequencies always higher than 50% in both study areas (annual average = 69.98%). Most of the 35 species of grasses assembled for the reference collection (91.43%) were identified in the pellets. Nevertheless, only six of these were consumed in proportions greater than 5%, being Anthoxanthum odoratum, Secale cereale and Agrostis spp. the species ingested in higher frequencies. The rate of grasses consumption reached 80.69% in winter but decreased in summer to around 55%. In this season, a concurrent rise in the ingestion of other plant groups, like herbs and shrubs, and of plant inflorescences was observed. This work provides the first results on the Iberian hare’s diet on mountain ecosystems, and suggests that the Iberian hare diet in a mountain ecosystem is similar to the observed in L. europaeus and L. timidus.

Keywords

Lepus granatensisDietFecal analysisMicrohistological techniquesIberian Peninsula

Introduction

The Iberian hare (Lepus granatensis) is an endemic species of the Iberian Peninsula. It is distributed throughout Portugal and most of Spain, being parapatric in northern Iberia with two other hare species, the brown hare (L. europaeus) and the broom hare (Lepus castroviejoi). Although the Iberian hare is common and even abundant in some locations, its populations have been declining in other areas, namely in the north of the Iberian Peninsula (Ballesteros et al. 1996; Duarte 2000). Several factors are considered responsible for this regression. However, the main reasons pointed out are over hunting and the loss of habitat diversity caused by the intensification of agriculture or by the expansion of homogenous shrub and forest areas into traditional agricultural patches (Ballesteros et al. 1996). Population decline has also been observed in other hare species in Europe, the main factor pointed being the loss of habitat diversity, caused by agricultural intensification (Dingerkus and Montgomery 2002; Vaughan et al. 2003; Smith et al. 2005; Reichlin et al. 2006).

The ability to propose specific conservation measures to reverse species regression is dependent upon the knowledge of their ecological requirements. Within these, understanding of the feeding ecology is of great importance as it should help to comprehend the species response to current habitat changes.

The dietary requirements of several hare species has been widely studied in Europe and North America. Studies on the brown hare, L. europaeus (e.g., Frylestam 1986; Chapuis 1990; Homolka and Heroldova 2003; Reichlin et al. 2006; Puig et al. 2007), on the mountain hare, L. timidus (e.g., Johannessen and Samset 1994; Wolfe et al. 1996; Dingerkus and Montgomery 2001), and on the black-tailed jackrabbit, L. californicus (e.g., Maccracken and Hansen 1982; Johnson and Anderson 1984) showed that grasses are generally the main component of their diet. However, available data also suggests the occurrence of temporal and spatial variation in the diets depending on food availability.

In contrast, and although some research has been carried out on the ecological requirements of the Iberian hare, there is very scarce information about their diet. Most of the studies on this species have focused mainly on taxonomy (e.g., Palacios 1989), genetics (Alves et al. 2000, 2003; Estonba et al. 2006; Melo-Ferreira et al. 2005, 2007), reproduction (Alves et al. 2002; Alves and Rocha 2003; Farfan et al. 2004), and distribution (e.g., Palacios and Meijide 1979). Few studies have been performed on the ecology of this species and these refer essentially to plain and crop areas (Calzada and Martínez 1994; Carro 2005).

In this work, we aim to determine the diet of two populations of Iberian hares in different mountain habitats by microhistological pellets analysis and to investigate its temporal variation patterns throughout a year.

Materials and methods

Study area

The study was carried out in the Natural Park of Serra da Estrela, between November 2001 and October 2002. This natural park is located in Central Portugal (40°15′–40°17′30″N; 7°15′–7°50′W) and is a part of the Iberian Central mountain system. Its geographical location and topography places Serra da Estrela under the influence of both Atlantic and Mediterranean climates which favors the occurrence of high habitat diversity. The two study areas, Santinha and Ensemil, are included in the Supramediterranean bioclimatic zone (Jansen 2002). Percentage covers of different habitats in both study areas are presented in Table 1. Santinha is a plateau located at about 1,500 m above sea level, composed predominantly by scrubland dominated by a subspecies of Spanish heath, Erica australis subsp. aragonensis, yellow rockrose, Halimiun lasianthum subsp. alyssoides, Pterospartum tridentatum, and small furze, Ulex minor. This habitat occupies nearly 85% (Table 1) of the area and includes small patches of herbaceous plants. Santinha also includes some small areas of natural grassland and a pine forest mainly composed by Pinus silvestris in the southeast of the area. Ensemil is a cereal plateau located at about 1,100 m above sea level. It is a heterogeneous area where traditional agriculture is still carried out, consisting mainly of dry crops of cereal rye (Secale cereale) in a set aside system. Shrub land of Portuguese broom (Cytisus striatus), yellow rockrose, and small furze is the predominant habitat (Table 1), since it progressed into some abandoned agricultural patches. Some areas were recently transformed in broad-leaf trees plantations such as oak tree (Quercus robur) and European chestnut (Castanea sativa). Both study areas have extensive cattle grazing.
Table 1

Habitat type percentage cover in both study areas, Santinha and Ensemil

Habitat type

Santinha

Ensemil

Agricultural pastures/crops

0

20.0

Natural Pastures

4.7

1.2

Scrublanda

84.4

5.9

Shrubs

4.3

55.9

Broadleaf woodland

0.5

7.5

Conifer woodland

5.7

8.9

Rocky areas

0.4

0.2

Urban areas

0

0.5

aComposed by shrubs on average less than 50-cm height

Plant reference collection

An epidermis reference collection of the majority of plants present in both study areas was prepared using a mechanical detachment method (Maia et al. 2003) and microphotographs. A collection of 166 plant species was established. Reference slides of the different plant parts (stem, leaf, inflorescence, fruit and seed) were photographed at ×200 magnification.

Fecal pellet collection and analysis

Diet analysis was carried out through microhistological pellets analysis. Fresh pellets were collected on a monthly basis, in twenty four 50-m2 plots spatially distributed throughout each study area and stratified by habitat type. The samples collected were labeled and frozen before further analysis.

For each alternate month, a sample of 15 to 20 pellets, of various sizes and formats, was analyzed, in order to maximize the probability of sampling different individuals (Chapuis 1990). The sample was milled through a 3-mm screen, to reduce variation in fragment size, and cleared in a diluted NaOH solution for 2 h (Vavra and Holecheck 1980). To clean the sample of dust particles, that could obscure fragment identification, it was washed over a 63 μm sieve (Bullock 1985). Finally the sample was colored with Bismarck Brown. From the resulting material, 40 systematic sub-samples were taken (using a grid) and mounted on microscope slides. The first ten fragments of each slide were identified by comparison with the reference collection, giving a total of 400 epidermal fragments per sample (Chapuis 1990). The key criteria used were characteristics of epidermal cells, cell wall, stomata, trichomes, and cellular inclusions. Most epidermal fragments were identified to the species level. However, due to some deterioration or similarity between taxa, some fragments were included in broader taxonomical groups or even classified as unidentified, when identification was impossible. Fragments were also classified according to the plant part (stem, leaf, inflorescence, flower, fruit and bulb).

Data analysis

Results were expressed as relative frequency of plants in each sample (number of fragments per plant species or group divided by total number of fragments per sample and multiplied by 100). Six plant groups were considered for the analysis: grasses, rushes, other monocotyledons, herbs, shrubs, and broad-leafed trees. The effect of location and month in the diet was analyzed using the G-test of independence (Sokal and Rohlf 1981). For this analysis, the items rushes, other monocotyledons, and broad-leafed trees were grouped in order to avoid zero values.

Diet diversity in both areas was assessed using the Brillouin diversity index (Margalef 1995). This index identifies the diversity of plant species that appear in each site, in relation to the maximum diversity possible in the sample. Evenness was derived from the Brillouin diversity index, through the formula: J = H′ / log2S, where: (H′) is the Brillouin diversity index and (S) the maximum diversity for each sample. This parameter measures the homogeny in distribution of the species consumed in each sample and varies from 0 to 1 (values greater then 0.5 represent high evenness).

Schoener’s overlap index was used to assess the diet similarity between locations (Schoener 1968). This index quantifies the resemblance of the diets, in terms of species composition and proportions, and varies from 0 to 100 (value that indicates equal diets).

Results

A wide range of plant species was eaten by hares in both study sites. Of the 166 plant species collected in the two study areas for the reference collection, 116 species were detected in hare’s diet. However, most of them were consumed in low frequencies and only a small fraction was ingested at high rates.

Brillouin diversity index were similar in the two study areas: 3.79 (±0.09) for Santinha and 3.72 (±0.13) for Ensemil (Table 2). Although a significant higher number of species was consumed in Ensemil (Santinha: 42.70; Ensemil: 52.50; t = 3.02; 5; p < 0.05), evenness was significantly higher in Santinha (0.70 ± 0.01) than Ensemil (0.65 ± 0.02; t = 2.46; 5; p < 0.05) which explains the similar diversity index values in the two study areas (Table 2). Nevertheless, these results indicate that hare’s diet is highly diversified in both areas with a high number of plant species being generally eaten in similar proportions.
Table 2

Relative frequencies of plant species identified in fecal pellets from the two study areas (S Santinha, E Ensemil) assembled by plant group (species with relative frequencies lower than 2% are included in the class other of each group). Brillouin diversity index, number of species identified and evenness are also presented

Month

Dec 01

Feb 02

Apr 02

Jun 02

Aug 02

Oct 02

Annual average

Study area

S

E

S

E

S

E

S

E

S

E

S

E

S

E

Agrostis hesperica

3.50

3.75

1.25

1.25

3.75

4.75

0.00

0.00

0.25

0.00

2.50

1.50

1.88

1.88

Agrostis spp.

2.75

9.25

3.00

11.50

1.25

2.00

7.25

16.25

19.75

12.25

10.75

2.00

7.45

8.88

Anthoxanthum aristatum

0.25

1.75

0.00

0.00

0.50

0.00

0.00

0.50

0.00

0.75

0.00

3.75

0.12

1.12

Anthoxanthum odoratum

11.75

0.00

9.75

1.75

22.75

3.50

10.50

0.00

1.25

0.50

4.75

0.50

10.13

1.04

Bromus hordeaceus

2.50

0.25

0.00

0.25

0.00

0.00

1.00

0.25

0.25

0.50

1.25

0.50

0.83

0.29

Corynephorus canescens

0.00

0.25

0.00

1.50

0.00

0.00

2.00

1.00

3.00

1.00

0.25

0.75

0.88

0.75

Cynosurus echinatus

4.75

1.00

3.75

0.50

1.50

2.50

0.00

0.25

0.00

0.00

2.50

0.50

2.08

0.79

Dactylis glomerata

0.00

2.50

3.50

1.50

2.00

2.25

0.25

0.00

0.50

0.25

1.00

2.75

1.21

1.54

Festuca spp.

3.25

1.75

3.50

2.75

2.00

0.25

1.00

0.50

0.25

0.75

1.50

0.00

1.92

1.00

Holcus annus subsp. Annus

1.75

1.50

2.75

1.75

1.75

2.75

0.00

0.50

0.00

0.50

3.00

0.50

1.54

1.25

Holcus lanatus

8.00

4.00

6.00

3.50

5.00

3.00

0.50

1.25

0.00

0.00

3.00

0.75

3.75

2.08

Holcus spp.

4.25

2.75

1.75

1.00

3.50

5.25

0.00

0.50

0.75

0.25

4.75

1.50

2.50

1.88

Hordeum murinum subsp. Murinum

0.25

0.25

0.50

0.75

0.00

5.50

0.50

0.50

0.25

0.00

0.25

0.00

0.29

1.17

Micropyrum spp.

1.00

0.75

4.00

1.75

0.25

1.25

1.00

1.25

1.00

2.00

1.50

3.50

1.46

1.75

Poa bulbosa

0.00

0.00

1.75

0.25

1.50

1.25

2.75

1.25

6,75

9.25

2.25

0.25

2.50

2.04

Secale cereale

0.25

6.00

0.75

6.75

3.50

6.25

0.25

0.25

0.00

0.25

3.25

12.25

1.33

5.29

Vulpia muralis

9.50

2.25

4.25

5.75

8.00

5.50

0.00

0.00

1.00

0.25

12.00

2.25

5.79

2.67

Other grasses

34.75

38.25

33.00

36.00

17.00

28.75

22.75

34.00

22.75

28.00

27.50

30.50

26.29

32.58

Total grasses

88.50

76.25

79.50

78.50

74.25

74.75

49.75

58.25

57.75

56.50

82.00

63.75

71.96

68.00

Luzula lactea

0.00

0.00

1.00

0.00

3.00

0.50

0.00

0.00

0.00

0.00

2.50

0.00

1.08

0.08

Total rushes

0.00

0.00

1.00

0.00

3.00

0.50

0.00

0.00

0.00

0.00

2.50

0.00

1.08

0.08

Liliaceae

0.25

0.50

0.75

0.25

0.25

1.00

0.00

0.25

1.00

1.00

0.25

2.50

0.42

0.92

Other monocotyledons

0.00

0.50

1.50

0.25

0.50

0.25

0.00

0.25

0.75

0.75

0.00

0.25

0.46

0.38

Total other monocotyledons

0.25

1.00

2.25

0.50

0.75

1.25

0.00

0.50

1.75

1.75

0.25

2.75

0.88

1.29

Helianthemum aegyptiacum

0.00

0.25

0.00

0.00

0.00

0.50

3.00

0.25

2.75

3.75

0.00

0.00

0.96

0.79

Polygala serpyllifolia

0.00

0.00

0.00

0.00

0.00

0.75

5.75

11.00

2.00

2.50

0.00

1.25

1.29

2.58

Polygala spp.

0.00

0.25

0.00

0.25

0.00

0.25

0.75

2.00

0.25

0.75

0.25

0.75

0.21

0.71

Rumex acetosella subsp. Angiocarpus

0.00

0.25

0.00

4.75

0.00

1.50

0.00

0.00

0.00

0.00

0.00

0.50

0.00

1.17

Cariophyllaceae

2.00

0.75

4.00

1.25

2.25

2.75

3.00

1.50

1.00

1.00

1.25

0.25

2.25

1.25

Hypochaeris radicata

0.00

4.00

0.00

0.50

0.00

3.25

2.75

2.50

1.00

2.75

0.25

3.75

0.67

2.79

Other Compositae

0.00

0.00

0.25

1.00

0.25

2.75

4.00

3.75

3.25

5.00

0.75

5.50

1.41

3.00

Leguminosae

1.00

0.50

0.50

1.00

0.25

2.50

1.50

3.00

1.25

0.50

0.25

0.50

0.79

1.33

Rinanthus minor

0.00

0.50

0.00

0.00

0.00

0.00

3.25

0.00

1.75

0.25

1.25

0.25

1.04

0.17

Other Scrophullariaceae

1.25

0.00

1.25

0.00

0.50

0.00

2.25

0.00

0.00

0.00

1.50

0.00

1.12

0.00

Other herbs

0.75

0.25

0.75

1.00

0.25

2.25

5.50

3.25

1.50

1.75

0.00

2.75

1.46

1.88

Total herbs

5.00

6.75

6.75

9.75

3.50

16.50

31.75

27.25

14.75

18.25

5.50

15.50

11.21

15.67

Erica spp.

0.25

0.25

0.25

0.25

0.50

0.00

0.00

0.00

2.50

0.50

0.25

0.50

0.62

0.25

Retama monosperma

0.00

0.00

0.25

0.25

2.75

0.00

2.25

0.25

0.00

0.25

0.25

0.25

0.92

0.17

Ulex minor

0.25

1.50

0.00

0.00

2.25

0.25

1.50

0.50

1.50

7.75

0.50

7.00

1.00

2.83

Other Leguminosae

1.75

1.75

3.50

1.00

7.50

0.25

1.75

0.25

2.25

0.50

1.50

0.25

3.04

0.67

Other shrubs (Ericaceae)

0.00

0.00

0.00

0.25

0.00

0.25

0.00

0.00

0.75

0.25

0.25

0.50

0.17

0.21

Total shrubs

2.25

3.50

4.00

1.75

13.00

0.75

5.50

1.00

7.00

9.25

2.75

8.50

5.75

4.12

Fagaceae

0.00

4.25

0.00

1.00

0.00

0.00

0.25

0.50

7.50

1.25

1.00

1.25

1.46

1.38

Total broad-leaf trees

0.00

4.25

0.00

1.00

0.00

0.00

0.25

0.50

7.50

1.25

1.00

1.25

1.46

1.38

Unidentified epidermis

4.00

8.25

6.50

8.50

5.50

6.25

12.75

12.50

11.25

13.00

6.00

8.25

7.67

9.46

Total number of species

36

40

40

51

36

57

52

50

48

62

44

55

42.70

52.50

Brillouin diversity index

3.50

3.48

3.71

3.57

3.69

4.16

4.11

3.29

3.76

3.86

3.94

3.95

3.79

3.72

Evenness

0.68

0.65

0.70

0,63

0.71

0.71

0.72

0.58

0.67

0.65

0.72

0.68

0.70

0.65

Diet composition

Grasses were the major component of hare’s diet throughout the year in both sites, contributing to 69.98% of the average annual diet (Table 2, Fig. 1). The most consumed grasses were Agrostis spp., which represented 10.04% of the diet in both study areas. In Santinha, Anthoxanthum odoratum and Vulpia muralis were also ingested in high frequencies, making up 10.13% and 5.79% of the annual diet in this area (Table 2). S. cereale composed 5.29% of the annual diet in Ensemil (Table 2). The second most abundant plant group was herbs, representing 13.44% of the average annual diet. From this group, the species Polygala serpyllifolia was the most consumed in both areas, making up 1.94% of the overall diet (Table 2).
https://static-content.springer.com/image/art%3A10.1007%2Fs10344-008-0181-z/MediaObjects/10344_2008_181_Fig1_HTML.gif
Fig. 1

Relative frequencies of plant groups identified in fecal pellets in both studies areas: a Santinha, b Ensemil

Shrubs were ingested in lower proportions, 4.94% of the diet in both areas. U. minor accounted for 1.92% of the diet (Table 2, Fig. 1). Broad-leaf trees, rushes, and other monocotyledons were minor components of the annual diet, comprising only 3.08% (Table 2, Fig. 1).

Vegetative plant parts were generally the major component of the hare diet throughout the year, comprising 65.52% of the diet. Of these, leafs were the most consumed (57.81%) followed by stems (7.48%; Fig. 2). Reproductive parts represented 28.21% of the annual diet, inflorescences being the most ingested item (22.52%; Fig. 2).
https://static-content.springer.com/image/art%3A10.1007%2Fs10344-008-0181-z/MediaObjects/10344_2008_181_Fig2_HTML.gif
Fig. 2

Relative frequencies of plant components identified in fecal pellets in both studies areas a Santinha, b Ensemil

Variation between sites

There was no significant difference in the annual group consumption between the two locations (G-test of independence; G = 4.65; 3; NS). Grasses contributed highly to hare’s diet in both sites, forming 71.96% of the diet in Santinha and 68.00% in Ensemil. Herbs and shrubs were also similarly consumed in both areas comprising 16.96% of the diet in Santinha and 19.79% in Ensemil. The other groups, ingested in lower proportions, showed also parallel values (Fig. 1).

Schoener similarity index of plant species ingested between the two locations ranged from 52.13 to 69.38. This indicates that although the diets of the two study areas presented analogous intakes of the different plant groups and had similar diversity indexes and evenness (see above), they were not very similar in terms of plant species composition.

The annual ingestion of the plant parts presented significant differences between the two study sites (G-test of independence; G = 21.95; 3; p < 0.001). Vegetative parts had higher expression in hares annual diet in Santinha (Santinha: 72.92%; Ensemil: 58.12%), while reproductive parts were consumed in greater proportions in Ensemil (Santinha: 20.96%; Ensemil 35.46%; Fig. 2).

Seasonal variation

The consumption of the different plant groups varied significantly throughout the year in both study areas (G-test of independence; Santinha: G = 349.84; 15; p < 0.001; Ensemil: G = 180.58; 15; p < 0.001) (Fig. 1). Grasses frequency in the diet reached its highest value in December (82.38%) and decreased in summer (June and August) to 55.56%. During this period, a concurrent rise of herbs occurred, from values of 7.06% in winter (December and February) to 23.00% in summer. There was also a slight increase in the ingestion of shrubs, from 2.87% on average in winter to 5.69% on average in summer (Fig. 1).

Despite the significant variation in groups’ intake, the species diversity index was found to be quite similar throughout the year. Nevertheless, it presented some seasonal variation and although the indexes were similar in both areas (see above), they varied differently throughout the year in each study area (Table 2).

Similarity indexes were calculated to assess similarity of diets in terms of species composition between the different months in both areas. The values obtained varied between 37.65 and 77.00 in Santinha and 48.65 and 75.37 in Ensemil. The highest levels of similarity were found between the winter months in both areas (Santinha: 77.00; Ensemil: 75.37). Summer months regimes (June and August) were not very similar (Santinha: 61. 25; Ensemil: 63.75) and also presented low similarity with other months’ diets (Santinha: 48.25; Ensemil: 56.88).

Plant part relative frequency in the diet also varied significantly throughout the year in both study areas (G-test of independence; Santinha: G = 683.85; 15; p < 0.001; Ensemil: G = 391.07; 15; p < 0.001). Leaves were highly ingested in autumn (October) and winter (on average 69.7%; Fig. 2). In the summer, there was a reduction in leaves consumption (to 34.00%) and an increase in the intake of reproductive parts, mainly of inflorescences, from 13.60% to 40.38%. Stem and other plant parts were also slightly more ingested in summer (Fig. 2).

Discussion

The diet of the Iberian hare, in Serra da Estrela, is mainly composed of grasses, varying between a minimum of 49.75% (June) and a maximum of 88.50% (December). Despite the different habitat composition of the two study areas (see Table 1), grasses ingestion is similar in both areas. Although Santinha has a lower amount of grasses available than Ensemil, since this area is mainly composed by scrubland, there is no significant differences in grasses ingestion in both sites, suggesting that Iberian hares have a preference for this plant group. These results are in concordance with those found in a study on Iberian hare in southern Spain, in a Mediterranean shrubland and marshland habitat, where grasses was the group ingested in higher frequencies (Carro 2005, Table 3). Several studies conducted on the diet of L. europaeus indicate, as well, grasses as the main component (e.g., Frylestam 1986; Chapuis 1990; Wray 1992). In particular, Wray (1992), in England, found grasses relative frequencies to fluctuate between 59.28 and 88.97%, values that are similar with those obtained in the present work. Studies on the Irish hare (L. timidus hibernicus) also found grasses to be a very important group in their diet, with values generally higher than 50% (Tangney et al. 1995; Wolfe et al. 1996; Dingerkus and Montgomery 2001).
Table 3

Relative frequencies of grasses on the diet of different hare species, obtained using the method of microhistological pellet analysis

Authors

Species

Country

Period

Relative frequency of grasses (%)

Homolka 1982

Lepus europaeus

Czech Republic

Annual average

59.50

Winter

36.05

Spring to autumn

71.15

Homolka 1987

Lepus europaeus

Czech Republic

Annual average

60.50

Wray 1992

Lepus europaeus

England

Annual average

72.07

Dingerkus and Montgomery 2001

Lepus timidus hibernicus

Ireland

Annual average

71.43

Tangney et al. 1995

Lepus timidus hibernicus

Ireland

Annual average

53.32

Wolfe et al. 1996

Lepus timidus hibernicus

Ireland

Annual average

94.03

Johnson and Anderson 1984

Lepus californicus

USA

Annual average

63.90

Maccracken and Hansen 1982

Lepus californicus

USA

Annual average

26.00

Spring to summer

43.00

Autumn to winter

9.00

Carro 2005

Lepus granatensis

Spain

Annual average

52.60

Present study

Lepus granatensis

Portugal

Annual average

69.98

Although it seems that hares show some preference for a particular plant group (grasses), the diet is highly diversified in terms of species composition. Our results are similar to those found by Dingerkus and Montgomery (2001) in the Irish mountain hare diet, however, a higher number of species is ingested by Iberian hares. Of the 35 grass species identified in the study area, 32 (91.43%) were found on the diet, even though only six have proportions higher than 5%. This indicates that a high number of species is evenly consumed at low frequencies, which explains the high diversity indexes obtained. Studies on black-tailed jackrabbits (L. californicus) also present diets based on a wide variety of grasses, being high densities associated with areas with high proportions of grass cover (Johnson and Anderson 1984).

Within the grass species consumed at higher frequencies, A. odoratum, Agrostis spp., Poa bulbosa and S. cereale were the most ingested by Iberian hares. The first two are very common grasses in natural pastures, being also referred as part of L. timidus diet in several studies (e.g., Johannessen and Samset 1994; Wolfe et al. 1996; Dingerkus and Montgomery 2001). Cereal rye crops are important in hare’s diet mainly in Ensemil in autumn and winter. In an area of intensively used arable land in Lower Austria, Reichlin et al. (2006) also found that brown hares preferred arable crops in these seasons. During this period, grasses are in an early phenological state which, according to Butet et al. (1989), can explain their selection. Moreover, the cereal crops areas are largely used by Iberian hares in winter, since they can provide forage and rapid escape from predators (Calzada and Martinez 1994).

Although the present study refers to a mountain area, the annual amount of snow cover in both study areas is small. Therefore, cereal crops and grasslands were almost always available. This fact would explain the observed high amount of grasses ingested during winter, in contrast to that reported in several studies performed on mountain hare or brown hares in areas of intense snow cover, which found hares to ingest a higher amount of shrubs and woody plants during this season (Homolka 1982; Hulbert et al. 2001; see also Table 3).

Iberian hare diet in summer differs from the other periods. In this season, a significant decrease in grasses consumption was complemented with the ingestion of alternative plant groups, like herbs and some shrubs. Additionally, a significant higher ingestion of reproductive plant parts, namely inflorescences, was observed in this season. This seasonal pattern of the diet was also reported in other hare species in Europe (Brown hare: Homolka 1982; Chapuis 1990; Wray 1992; and Mountain hare: Wolfe et al. 1996), being generally associated with the higher nutritive value of alternative groups and reproductive plant parts.

In Mediterranean ecosystems, summer is characterized by very high temperatures and low rainfall. Thus, a decrease of crude protein content in herbaceous plants, as well as a decrease in water and biomass and an increase in fiber content is observed (Alves and Rocha 2003). On the other hand, dicotyledonous plants generally have higher protein content and lower fiber content (Kuijper et al. 2004). Therefore, it seems that the higher consumption of herbs and shrubs, as well as of reproductive plant parts by Iberian hares observed in summer can be associated with a compensation strategy for the lower quality of the vegetative part of grasses in this season.

In contrast to that observed in the Wild rabbit, Oryctolagus cuniculus algirus, (the only other lagomorph that occurs in Portugal) that ceases its reproductive activity in the summer (Gonçalves et al. 2002) when environmental harsh conditions (high temperatures, low food quality) are observed, the Iberian hare breeds continuously throughout the year (Alves et al. 2002). Therefore, the significant seasonal changes in Iberian hare’s diet could reflect an attempt to compensate for the lower quality of the available food in the summer in order to maintain the reproductive activity during this season. However, studies on the diet of wild rabbit in Portugal also suggest this species ability to adapt its feeding strategies in order to ensure a high-quality diet throughout the year (Marques and Matias 2001; Martins et al. 2002) which is not associated with continuous breeding. Hence, it would be useful to make a comparative study of the diet of these two species in Portugal in order to assess if there are nutritional differences that could support the continuous breeding observed in Iberian hares.

On the other hand, comparative studies of the digestive strategies of Brown hare and domestic rabbits (O. cuniculus) report that there are differences in nitrogen digestion efficiency between these species (Kuijper et al. 2004). However, hares are reported to compensate their lower digestive efficiency by increasing the intake and the passage rate of the food through the digestive tract (Kuijper et al. 2004). A previous study by Kronfeld and Shkolnik (1996) compared digestibility and food intake by brown hares from southern France and by Cape hares (L. capensis) in desert habitats. These authors verified that Cape hares digested the high-fiber plant material more efficiently and required less food, suggesting an adaptation to the life in the desert. This species and L. granatensis have similar body weights, litter size, and breeding activity. So, as already proposed by Alves and Rocha (2003) it can be possible that L. granatensis has similar physiological adaptations as those reported by Kronfeld and Shkolnik (1996) for Cape hare in desert habitats. Therefore, it would be valuable to assess the digestibility and food intake by Iberian hares.

Habitat changes that lead to a loss of habitat diversity are considered an important cause in the decline of hare populations (Dingerkus and Montgomery 2002; Vaughan et al. 2003; Smith et al. 2005). Moreover, diverse landscapes and natural pastures are considered essential for supporting prosperous populations of Iberian hares (Calzada and Martinez 1994). The present study sustains this view, since it shows that Iberian hares have a diversified diet throughout the year and that they shift their food composition in summer by ingesting alternative species of herbs and shrubs. Therefore, considering current habitat changes in Portugal due to modifications in agricultural and forest management practices and the high frequency of fires, efforts should be made to maintain habitat diversity and hence sustain Iberian hare populations.

Acknowledgements

This research was partially funded by FCT—Fundação para a Ciência e a Tecnologia (SFRH/BM/3962/2001) and by ICNB (Portuguese Institute for Conservation and Biodiversity).We wish to thank the Director of Natural Park of Serra da Estrela for all the support given during field work. We thank J. P. Pires, S. Oliveira, A. Magalhães, J. Riquinho and V. Ernwienv for their assistance in field work and P. Alves for helping in plant identification. We also thank F. Barreto and R. Silva from the Botanic Department for all the support given during laboratory work, and C. Ferreira and M. Carretero for all their comments.

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© Springer-Verlag 2008