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The Iberian ibex is under an expansion trend but displaced to suboptimal habitats by the presence of extensive goat livestock in central Spain

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In this paper an updated distribution of the Iberian ibex (Capra pyrenaica, Schinz 1838) in the central Spanish region of Castile–La Mancha is shown. The species is present in 19% of the study region, and in areas not cited so far in the literature. A detailed analysis of habitat suitability was also carried out, applying a new methodology, Ecological-Niche Factor Analysis, which uses presence data to build a habitat suitability map of a given species. As livestock activity is quite intense in the region, the presence of a potential competitor, the domestic goat (Caprahircus), was included in the analyses. Factors affecting ibex relative abundance were determined by means of a nested stepwise multiple regression, where livestock presence/absence was the nested factor. The presence of livestock has a negative effect on ibex relative abundance, causing the ibex to select areas of poor, sparse vegetation, cultivated lands and forests, whereas in the absence of livestock, the ibex is mainly present in pasture–scrub lands and non-cultivated lands. Conservation implications of these results are discussed in the context of a Mediterranean region where extensive livestock grazing systems abound.
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Abstract In this paper an updated distribution of the Iberian ibex (Capra pyre-
naica, Schinz 1838) in the central Spanish region of Castile–La Mancha is shown.
The species is present in 19% of the study region, and in areas not cited so far in the
literature. A detailed analysis of habitat suitability was also carried out, applying
a new methodology, Ecological-Niche Factor Analysis, which uses presence data
to build a habitat suitability map of a given species. As livestock activity is quite
intense in the region, the presence of a potential competitor, the domestic goat
(Capra hircus), was included in the analyses. Factors affecting ibex relative abun-
dance were determined by means of a nested stepwise multiple regression, where
livestock presence/absence was the nested factor. The presence of livestock has a
negative effect on ibex relative abundance, causing the ibex to select areas of poor,
sparse vegetation, cultivated lands and forests, whereas in the absence of livestock,
the ibex is mainly present in pasture–scrub lands and non-cultivated lands. Con-
servation implications of these results are discussed in the context of a Mediterra-
nean region where extensive livestock grazing systems abound.
Keywords Biodiversity conservation ÆCapra hircus ÆCapra pyrenaica Æ
Livestock grazing system ÆHabitat displacement ÆHabitat suitability analysis Æ
Resource competition
Introduction
To conservation biologists it is of particular interest to determine the effects of
invasive species on the natural history of autochthonous ones (see Lodge 1993). A
particular example is that of exotic ungulates introduced in areas where they can
potentially compete with native ones (see, e.g., Cassinello et al. 2004). Among the
P. Acevedo ÆJ. Cassinello (&)ÆC. Gortazar
Instituto de Investigacio
´n en Recursos Cinege
´ticos (IREC),
CSIC, UCLM, JCCM, Ronda de Toledo s/n, 13005 Ciudad Real, Spain
e-mail: jorge.cassinello@uclm.es
123
Biodivers Conserv (2007) 16:3361–3376
DOI 10.1007/s10531-006-9032-y
ORIGINAL PAPER
The Iberian ibex is under an expansion trend
but displaced to suboptimal habitats by the presence
of extensive goat livestock in central Spain
Pelayo Acevedo ÆJorge Cassinello Æ
Christian Gortazar
Received: 9 August 2005 / Accepted: 20 February 2006 / Published online: 16 May 2006
Springer Science+Business Media B. V. 2006
former, livestock represent a particular instance (Voeten and Prins 1999), usually
underestimated by conservation biologists (Fleischner 1994). Although livestock
graze more than one-third of the world’s land area, and in many instances share
resources with native ungulates (see de Haan et al. 1997), evidences of a negative
impact on the latter are not conclusive and highly debated (e.g., Saberwal 1996;
Mishra and Rawat 1998; Madhusudan 2004; Young et al. 2005).
The development of large, relatively permanent, agriculture-based societies was
the primary event initiating livestock domestication about 10,000 years ago (Price
2002). With a few exceptions, ungulate domestication (e.g., cattle, sheep and goats)
mainly began in the Near East (Troy et al. 2001). The presence of livestock in
Europe goes back to Neolithic times, domestic sheep and goats showing up partic-
ularly in Mediterranean countries (see, e.g., Martı
´n Bellido et al. 2001).
The status and distribution of the Iberian ibex have been studied by several
authors, either in the whole peninsula (e.g., Granados et al. 2002;Pe
´rez et al. 2002)
or in some particular areas (e.g., Granados et al. 1998; Palomares and Ruiz-Martı
´nez
1993; Lasso De La Vega 1994;Pe
´rez et al. 1994; Gortazar et al. 2000). Concerning
Castile–La Mancha region, in central Spain, Granados et al. (2002) indicate that the
ibex is distributed exclusively in 11% of the region, whereas Pe
´rez et al. (2002)
distinguish 51 ibex population nuclei in Spain, out of which only 4 were located
in Castile–La Mancha: Serranı
´a de Cuenca, Caban
˜eros National Park, Sierra de
Alcaraz (connected to the well established ibex population of Sierra de Cazorla,
Segura y Las Villas Natural Park, it is supposedly in expansion), and Sierra Madrona
(a series of fragmented nuclei connected to other ones in Sierra Morena, Jae
´n
province).
Here, we analyse the current distribution and habitat use of the Iberian ibex
(Capra pyrenaica, Schinz 1838) in Castile–La Mancha. We have considered it
appropriate to use a political division to define our study area because in Spain
conservation field is partly ruled by regional governments. This region is charac-
terised by an intense livestock breeding activity, namely extensive sheep and goat
grazing systems (see Martı
´n Bellido et al. 2001). We have, thus, included in our
analyses the presence of the domestic goat (Capra hircus), a close relative of the
Iberian ibex and, therefore, expected to share feeding habits and ecological
requirements with it; to our knowledge, no comparative studies of diet and/or spatial
niche use have been made so far. Sheep, on the contrary, show a differing feeding
behaviour (Martı
´nez 2002) and probably their potential as competitor of the Iberian
ibex is less pronounced.
The spatial prediction of species distribution is an important tool for conser-
vation biology and management planning (e.g., Hortal et al. 2005; Whittaker et al.
2005). Developments of ecological and biogeographic theories have been trans-
lated into different methodologies, which are able to predict the distribution
ranges and habitat suitability of species (see Guisan and Zimmermann 2000;
Ferrier et al. 2002; Scott et al. 2002), using a wide variety of statistical approaches
and Geographical Information Systems tools (GIS) (e.g., Austin 2002; Rushton
et al. 2004). The use of a Digital Elevation Model (DEM) constitutes a basis for
generating maps of environmental variables (see Guisan and Zimmermann 2000),
as it has basic outcomes, such as altitude, slope or aspect, which influence the
distribution of the organisms. Furthermore, the use of digitalised land informa-
tion database, allows a more detailed analysis of factors determining species
distribution.
3362 Biodivers Conserv (2007) 16:3361–3376
123
Predictive models can easily be made from data of the presence and absence of a
given species (e.g., Osborne and Tigar 1992; Brito et al. 1999). Nevertheless, it is
necessary to distinguish true absences from a mere lack of information (Thuiller
et al. 2004; Arau
´jo et al. 2005). The determination of true absences of a given species
in a given area is the main problem of many animal presence/absence data sets
(Hirzel et al. 2002; Zaniewski et al. 2002). Thus, some techniques incorporate
presence-only data (Hortal et al. 2005), such as the relatively novel Ecological Niche
Factor Analysis (ENFA) (Hirzel et al. 2002). ENFA is used to determine habitat
suitability starting from the location of presence-only data. These maps are the result
of the location of a given species within the multidimensional environmental area
that is defined by considering all mapping units within the study area (Guisan and
Zimmermann 2000). These habitat suitability maps indirectly reveal the species
potential distribution (Hirzel et al. 2002). This approach is recommended when
absence data are not available (most data banks), unreliable (most cryptic or rare
species) or meaningless (invaders) (Hirzel et al. 2001), the subsequent results are to
be handled with caution (e.g., Brotons et al. 2004; Engler et al. 2004). Using these
data, this method characterises the realised niche of the species from a set of
environmental predictors. Thus, an application of the method could be interesting in
many domains: landscape management for endangered species, better knowledge of
unknown or inaccessible areas, or also better knowledge of ‘new species’ ecology
and/or distribution (e.g., Reutter et al. 2003; Gallego et al. 2004; Chefaoui et al.
2005). This method was originally assessed in the Alpine ibex (Capra ibex) (Hirzel
et al. 2002), but is currently widely used (see a list of publications at http://www.u-
nil.ch/biomapper/bibliography.html).
Apart from an updated distribution of the Iberian ibex in Castile–La Mancha, our
aim in this study is to carry out a detailed analysis of habitat suitability of the species
and determine which factors affect its abundance taking into account the influence of
livestock presence/absence.
Materials and methods
The study area
Located in central Spain, it corresponds with Castile–La Mancha political division
(U.T.M. 30S 294,348–681,063 4,208,706–4,575,340), which is placed at the southern
plateau of the Iberian Peninsula. Politically, the region is conformed of five prov-
inces (see Fig. 1), where the studzy species is distributed unevenly. Castile–La
Mancha is the Iberian region where game activity is more intense. It has a surface
area of 79,226 km
2
, which represents 15.7% of the whole Spanish territory. The area
devoted to game activity in this region is 70,000 km
2
(88% of its territory), big game
estates occupying 19,000 km
2
(Junta de Comunidades de Castilla—La Mancha,
http://www.jccm.es/medioambiente/mednat/cazapesca.htm).
The study region shows a typical Mediterranean continental climate, with dry
periods both in summer and winter, rains concentrated in autumn and spring,
and extreme temperatures during the hottest (summer) and coldest (winter) sea-
sons. Mediterranean woodland vegetation is present and it is formed of oak
trees (Quercus ilex) along with shrubs of different species (e.g., Q. coccifera,
Pistacia lentiscus,Cistus spp., Rosmarinus officinalis, etc.). Open lands with
Biodivers Conserv (2007) 16:3361–3376 3363
123
scattered trees (evergreen oak savannah like habitats), the so-called ‘‘dehesas’’, are
also common. In addition, pine woodlands (Pinus spp.) can also be found in some
elevated areas.
Apart from the Iberian ibex, other ungulate species that can be found free-
ranging in the study area are wild boar (Sus scrofa) and red deer (Cervus elaphus),
and to a lesser extent fallow deer (Dama dama), and roe deer (Capreolus capreolus)
(see, respectively, Rosell and Herrero 2002; Carranza 2002; Braza 2002; San Jose
´
2002).
The study species
The Iberian ibex is a wild goat endemic to the Iberian Peninsula. The IUCN (2004)
considered it as at Low Risk, but near threatened (LR/nt), whereas the existing
subspecies hold different qualifications. C. p. victoriae Cabrera, 1911 is Vulnerable
(VU D2), due to the few and small areas it inhabits (see Pe
´rez et al. 2002).
C. p. hispanica Shimper, 1848 is at Low Risk (LC/cd), but its viability depends on
current conservation programmes. This latter subspecies is widely distributed com-
pared to the former one (ibid). Two other subspecies were also distinguished, but
they are extinct nowadays: C. p. pyrenaica, Schinz 1838 and C. p. lusitanica, Schlegel
Fig. 1 Situation of the study area (Castile–La Mancha region in central Spain), the administrative
provinces concerned, and its division in 10 ·10 grids, showing the presence/absence of the Iberian
ibex
3364 Biodivers Conserv (2007) 16:3361–3376
123
1872 (ibid). However, the distinction of these subspecies has been questioned by
Manceau et al. (1999), who found no genetic differences between the two existing
subspecies.
The sampling method
Presence of ibexes in the study area was assessed by means of direct field obser-
vations and by carrying out surveys (n= 149) addressed to forest rangers and staff
from environmental agencies of the government of Castile–La Mancha region.
Information obtained by other naturalists was verified by visiting areas where ibexes
were reported. The sampling units were 10 ·10 km. UTM grid cells (n= 905).
Survey addressees were asked to draw in a map their work area and the range
occupied by the Iberian ibex, red deer, wild boar and livestock. A questionnaire was
given to them, where they indicated the status of the populations present, such as the
largest group size registered, a straightforward variable, easy to account for by field
watchers.
In order to assess ibex abundance, we firstly relied on forest rangers and envi-
ronmental managers’ indication of the largest group size registered. The Iberian ibex
is characterised by sexual segregation through most of the year, but the largest group
sizes are attained during the mating season (November–December) according to
Granados (2001), when ibexes are also more conspicuous. We have confirmed that
group sizes given in the questionnaire refer to mixed groups observed during the
mating season, when they may reflect population abundance in species showing
sexual segregation (see Toigo et al. 1996). In addition, we validated these data by
carrying out our own field surveys.
During September 2003, we performed 17 field surveys consisting of line transects
(e.g., Burnham et al. 1980), a methodology widely used to estimate relative abun-
dance of wild goats (e.g., Alados and Esco
´s1996;Pe
´rez et al. 1994). Average length
of line transects was 3 km., and they were carried out in the main areas where the
Iberian ibex is present in Castile–La Mancha, and during hours of maximum activity,
i.e. at dawn and at dusk (e.g., Alados 1986). We only registered female groups, and
used these data to test whether the largest group size obtained in the questionnaire
was a good estimate of ibex abundance (see Results).
Habitat suitability
The ENFA computes a habitat suitability model by comparing the ecogeographical
variables (EGVs) which characterise the locations where the species is detected with
those present in the whole study area (Hirzel et al. 2002).
Habitat suitability for the Iberian ibex was assessed in the area where the species
was more abundant according to the surveys, using 1 ·1 km UTM grid cells.
Twenty-seven EGVs were defined, including topographical features (e.g., altitude,
slope), land cover, and livestock presence (see Table 1), and normalised by a Box-
Cox transformation (Sokal and Rohlf 1981). We did not considered climatic vari-
ables because of the relative homogeneity of the study area on this matter, where
only slight differences can be registered, mainly due to topographic variations.
Average distances to each land cover classes were calculated for each sample unit by
means of ‘‘Distance Operator’’ tool (Idrisi32 v.32.21) (see Hirzel et al. 2002). The
topographic data from a DEM carried out by the Shuttle Radar Topography Mission
Biodivers Conserv (2007) 16:3361–3376 3365
123
(European Environment Agency 2000), with a spatial resolution of 90 m., was
extracted by overlaying the DEM with the cells of 1 ·1 km. in a geographic
information system (Idrisi32 v32.21) (see Hortal et al. 2001).
Firstly, the ENFA was run, by means of BioMapper software (Hirzel et al. 2001,
2004; see http://www.unil.ch/biomapper/). It computes a global marginality coeffi-
cient, expressing how, on all the EGVs, the species average differs from the global
average, and a global specialisation coefficient, expressing the ratio of global vari-
ance to species variance.
Formally, marginality is defined as the absolute difference between the global
mean and the species mean, divided by the standard deviations of the global dis-
tribution multiplied by a constant (see Hirzel 2001 for details). A value close to one
Table 1 Ecogeographical variables (EGVs) used in the ENFA
Codes Meaning Global
mean
Species
mean
Topografic
altitud_max Maximum altitude 507.24 0.95
Aspect Average orientation 98.49 0.87
Slope Average slope 2.82 1.44
Cultures
dist_agriculture Average distance to cultivated lands 2260.56 0.82
dist_agroforest Average distance to agroforest lands 11990.41 1.22
dist_annual_crops Average distance to annual crops 19572.28 0.63
dist_complex_cult Average distance to complex cultures 1933.19 0.64
dist_perm_irrigate Average distance to irrigated cultures 1368.97 0.42
Fruit tree
dist_fruit_tree Average distance to fruit tree cultures 4249.16 0.15
dist_olives Average distance to olive tree cultures 5388.66 0.04
dist_vineyards Average distance to vineyards 4714.15 1.25
Woodland
dist_broad_leav Average distance to broad leaves forests 4828.36 1.05
dist_mixed_forest Average distance to mixed forests 6194.78 0.72
dist_conniferous Average distance to conniferous forests 3021.63 )0.34
dist_wood_scrub Average distance to wood-scrub ecotones 1509.38 0.81
dist_sclerophyllous Average distance to sclerophyllous areas 1421.79 0.34
Scrubland
dist_moors_heath Average distance to moors and heaths areas 29133.07 0.56
Grassland
dist_natu_grass Average distance to natural grass lands 2706.51 0.39
Sparse veg.
dist_sparse_veg Average distance to sparse vegetation 12196.57 )0.32
dist_bare_rocks Average distance to bare rocks areas 24583.19 )0.05
Infrastructure
dist_village Average distance to villages 3217.65 0.84
dist_industr Average distance to industrial areas 11612.99 1.07
dist_road_rail Average distance to roads and rails 27601.89 0.74
Water
dist_river Average distance to rivers 10852.34 )0.09
dist_inland_marshes Average distance to inland marshes 20417.79 1.38
dist_water_bodies Average distance to water bodies 14409.52 0.09
Livestock
dist_goat_livestock Average distance to goat livestock 2515.05 0.07
Average values in the study region are shown (global mean), together with the standardized ones, as
provided by ENFA, in areas where the Iberian ibex is present (species mean). All values are in
metres, except for orientation, which is in degrees
3366 Biodivers Conserv (2007) 16:3361–3376
123
means that the species lives in a very particular habitat relative to the reference set.
Similarly, specialisation is defined as the ratio of the standard deviation of the global
distribution to that of the study species (Hirzel 2001). A randomly-chosen set of cells
is expected to have a specialisation of one, while any value exceeding that score
indicates some form of specialisation.
The factor coefficients for the marginality factor account for the marginality of a
given species in each EGV considered. It is measured as units of standards devia-
tions of the global distribution. The higher the absolute value of a coefficient, the
further the species departs from the average value of a given EGV. There are other
factors which express a degree of specialisation, where the higher the value, the
more restricted is the range of the study species on the corresponding variable
(Hirzel 2001).
Habitat use
Information obtained from the surveys was registered in 10 ·10 km. UTM grid
squares (n= 905) by means of Idrisi32 v32.21 software (Clark Labs, Clark Univer-
sity). For each UTM square the frequency of occurrence of 11 ecogeographical
variables (EGVs) were identified (see Table 2). These variables were obtained from
CORINE Land Use/Land Cover database, spatial resolution (pixel width) of 250 m
(European Environment Agency 1996). From this information we carried out both
the habitat use analysis and the study of the influence of goat livestock.
The analysis of the variables which determine habitat use (Table 2) by the Iberian
ibex was assessed by a nested stepwise multiple regression analysis, using domestic
goats presence/absence as the nested factor (e.g., Quinn and Keough 2002). The
Iberian ibex abundance was the response variable. We designed a three step pro-
cedure to clarify the significance of the variables and their interaction with goat
livestock on the Iberian ibex habitat use.
In total, 11 habitat factors were considered: (1) We discarded a number of vari-
ables with no statistical significance and avoided multicollinearity by using the
Table 2 EGVs used in habitat
use analysis for the Iberian
ibex relative abundance
dependent variable
The significance level of step 2
is provided (** P\0:01,
*P\0:05, n.s. = non-
significant). See text and
Table 1for more details
Variables Meaning Significance
Goat livestock Presence/Absence
of goat livestock
**
Highest altitude Maximum altitude (m) n.s.
Average altitude Average altitude (m) n.s.
Slope Average slope index n.s.
Cultures Frequency of cultures
per pixel
*
Woodland Frequency of woodlands
per pixel
**
Scrubland Frequency of scrublands
per pixel
**
Grassland Frequency of grasslands
per pixel
n.s.
Sparse vegetation Frequency of sparse
vegetations per pixel
**
Infrastructures Frequency of human
infrastructures per pixel
n.s.
Water reservoir Frequency of rivers per pixel *
Biodivers Conserv (2007) 16:3361–3376 3367
123
Spearman Rank Correlation coefficients. (2) Each of the independent variables
obtained from step 1 were then related to the dependent variable, ibex relative
abundance. Stepwise multiple regression analysis was used (Quinn and Keough
2002). (3) Variables that yielded P\0:05 in step 2 were integrated into a final model
which also included the nested factor of livestock presence. We carried out a nested
regression analysis and obtained a final model through a backward stepwise pro-
cedure. The level of significance for step 3 was set at 5%. The statistics package used
was SPSS 10.06.
Results
Species distribution according to the surveys
Information covering 97.68% of the whole Castile–La Mancha region has been
obtained from 149 surveys correctly filled in. Results showed that the Iberian ibex
is present in 19% of the study area (175 out of 905 sampling units). Five population
nuclei have been identified: Montes de Toledo mountain range, Sierra
Madrona—Sierra Morena, Alto Tajo—Serranı
´a de Cuenca, Casas Iba
´n
˜ez, and south
of Albacete (see Fig. 1). The species is more widely distributed in Albacete province
(it is present in 47% of the territory), followed by Guadalajara (21%), Cuenca
(15%), Ciudad Real (12%) and Toledo province (3%).
Habitat suitability
An habitat suitability map for the study species was carried out for the province of
Albacete, where the species was more abundant (see above). This meant a total
number of 15,384 1 ·1 km. UTM grid cells. Table 1shows average values for the
EGVs that define the habitat, both in the whole study area (global mean) and in the
area where ibexes were found (species mean, with standardised values). For the
ENFA analysis, the variable ‘‘average distance to non-irrigated lands’’ was discarded
due to its discontinuity. The three significant factors selected (out of 27) explained
87.6% global marginality and 75.2% global specialisation. Coefficients of relation-
ship between variables and each one of the three factors are shown in Table 3.
Global marginality was 2.03, and global tolerance was 0.49. The habitat suitability
map can be seen in Fig. 2. The first factor obtained, marginality factor, was essen-
tially associated to both high altitudes and slopes, and areas distant to agro-forest
lands, broadleaf woodlands, industrial areas, marshes and vineyards (see coefficients
in Table 3). Ibexes are extremely sensitive to shifts from their optimal conditions on
this axis. Next factors show a certain degree of specialisation, being associated to
areas distant to coniferous forests, sparse vegetation and human constructions, such
as roads and railways, but also close to annual crops lands. Factor 3 accounts for
19.2% of specialisation, so that information provided is much less accurate than that
of the other two factors (see Table 3).
Habitat use
Relative ibex abundance was assessed by the largest size group registered in each
UTM grid cell considered in the study area, and obtained from the questionnaire.
3368 Biodivers Conserv (2007) 16:3361–3376
123
Previously, we determined the validity of this measure by relating it to our own
average group size (see above). In our field surveys, we detected 36 ibex groups (167
animals were counted) from the 17 transects carried out in September 2003. The
average group size was 4.76 0.65, and it correlated with the largest group size
obtained in the questionnaire (Spearman Rank Correlation: n=9, q¼0:80,
P¼0:01), so that the latter can be considered as an estimate of ibex abundance.
Fig. 2 Habitat suitability map for the Iberian ibex in Albacete province. Observed Ibex distribution
is outlined. The arrow indicates a potentially suitable area not occupied by the ibex, and where
livestock is present
Table 3 Correlation between
ENFA factors and the
environmental descriptors
(EGVs)
Percentages indicate the
amount of specialization
accounted for by each factor.
Factor 1 is Marginality factor
Variable Factor 1
(87.6%)
Factor 2
(55.4%)
Factor 3
(19.2%)
altitud_max 0.24 0.01 0.10
Aspect 0.22 0.04 0.00
dist_agriculture 0.21 0.08 )0.02
dist_agro_forest 0.31 )0.09 0.32
dist_annual_crops 0.16 )0.26 0.16
dist_broad_leav 0.26 )0.02 0.00
dist_goat_livestock 0.02 )0.06 0.20
dist_coniferous )0.09 0.51 0.61
dist_industr 0.27 0.09 0.23
dist_inland_marshes 0.35 )0.02 )0.37
dist_road_rail 0.19 0.42 0.11
dist_sparse_veg )0.08 0.62 )0.27
dist_villages 0.21 )0.09 0.04
dist_vineyards 0.31 0.12 )0.14
dist_water_bodies 0.02 0.03 )0.34
dist_wood_scrub 0.20 )0.01 )0.01
slope 0.36 0.04 0.01
Biodivers Conserv (2007) 16:3361–3376 3369
123
Nested stepwise multiple regression analysis showed that livestock influences
habitat use of the Iberian ibex, relegating it to suboptimal vegetation areas (see
Table 4). In those grid cells where domestic goat livestock ranges in sympatry with
the ibex, the latter occupies preferentially cultivated lands, sparse vegetation areas
and forests; whereas in absence of livestock the ibex is mainly found in pasture–scrub
areas and non-cultivated lands. The marginal effect caused by distance to goat
livestock herds (see Factor 3 in Table 3), is exemplified in Fig. 2.
In Fig. 3the relationship between those variables which showed opposite direc-
tions, depending on the presence/absence of goat livestock, i.e. scrub land and cul-
tures, is shown.
Discussion
Here we have updated the Iberian ibex distribution in the region of Castile–La
Mancha (central Spain). A habitat suitability model has also been accomplished by
using the ENFA technique, particularly suitable for presence-only data of a given
species. Our results indicate that the Iberian ibex is not occupying its optimal habitat
in those areas where it shares its range with domestic goat herds.
On ibex distribution in the study region, it is noteworthy to point out a wider
presence in comparison with previous surveys (Alados 1997;Pe
´rez et al. 2002). A
plausible explanation is the expected increase of the species area of distribution
which is taking place nowadays, in part due to a natural increment of population
numbers due to habitat changes, game management translocations (Gortazar et al.
2000) or its recovery from past sarcoptic mange epizootics (Pe
´rez et al. 1997), and a
probable decrease of its hunting pressure caused precisely by the incidence of this
disease (see Garrido 2004).
Concerning risks associated to parasite infections of the ibex, the main agents are
host-inspecific, e.g., sarcoptic mange (Pe
´rez et al. 1997), so that they can infect any
ungulate species, among other mammals. Therefore, at high host densities, as it is the
case in areas with high livestock densities, the availability of habitat for these par-
asites increases, as does the risk of epizootics (see Acevedo et al. 2005).
Specific values for marginality and tolerance indexes are bound to depend on the
global set chosen as reference, so that a species might appear extremely marginal or
Table 4 Final model obtained
for the habitat use analysis for
the Iberian ibex relative
abundance dependent variable
(nested stepwise regression
output)
GL column refers to goat
livestock absence (A) and
presence (P). TE refers to the
typical error
Parameter GL Estimate TE tProbability
Intercept 3.07 0.86 3.58 <0.01
Scrub land (A) 0.88 0.31 2.88 <0.01
(P) )0.94 0.30 )3.13 <0.01
Cultures (A) )0.53 0.27 )2.47 0.01
(P) 0.89 0.19 4.67 <0.01
Wood land (A) )0.04 0.22 )0.20 0.84
(P) 0.81 0.22 3.65 <0.01
Sparse vegetation (A) )0.27 3.10 )0.09 0.93
(P) 1.45 0.45 3.19 <0.01
Water (A) 5.62 4.02 1.40 0.16
(P) 12.55 6.14 2.04 0.04
Goat livestock (A) )4.54 1.23 )3.69 <0.01
(P) 0 0.00 –
3370 Biodivers Conserv (2007) 16:3361–3376
123
specialised on the scale of a whole country, but much less so a subset of it (Hirzel
et al. 2002). According to habitat suitability analysis carried out the Iberian Ibex is
highly marginal in the studied area, and presents a medium tolerance, evidencing
that, although it is placed in marginal areas in Castile–La Mancha, it seems to
tolerate habitat changes, therefore compensating its marginality with the expansion
to areas of relatively suboptimal habitat.
In our study, livestock seem to compete and displace the Iberian ibex from its
optimal habitat, i.e. pasture–scrub lands (e.g., Chirosa et al. 2002), in those grid
cells where livestock is present (see Fig. 2). We have no data on social avoidance
between both species, so that future research should be focused on confirming this
apparent ecological displacement. Similar conclusions were obtained from a study
carried out in the Great Basin, where pronghorn (Antilocapra americana) avoided
areas grazed by sheep during winter until spring-regrowth occurred, and favoured
areas temporarily rested from sheep use (Clary and Holmgren 1982; Clary and
Beale 1983).
This apparent displacement of the Iberian ibex to suboptimal habitats by
livestock presence is confirmed in our nested factor analysis of habitat use. The
results obtained indicate that the ibex occupies different habitats depending on
the presence of domestic goats. When they are present, as seen in the previous
analysis of habitat suitability, the ibex is preferentially found in suboptimal hab-
itats, according to its resource requirements (see, e.g., Chirosa et al. 2002),
Fig. 3 Relationships between Iberian ibex relative abundance and two EGVs which show opposite
directions depending on the presence/absence of goat livestock, i.e. scrub land and cultures (see
Table 4)
Biodivers Conserv (2007) 16:3361–3376 3371
123
i.e. sparse vegetation, cultures and woodlands; whereas when livestock is absent,
the ibex mainly uses scrub lands and non-cultivated areas, where food availability
according to its diet is higher (e.g., Martı
´nez and Martı
´nez 1987; Martı
´nez 2000).
The question is whether both species, the ibex and the domestic goat, actually
compete for resources. Resource partitioning is defined as the differential use by
organisms of resources such as food and space (Schoener 1974; Begon et al. 1996),
and may explain how species coexist despite extensive overlap in ecological
requirements (Hutchinson 1959; MacArthur and Wilson 1967; MacArthur 1972; May
1973). On the contrary, competition is considered to be the major selective force
causing this differential use of resources (Schoener 1974,1986).
As livestock range and distribution exceed any natural expansion process, they
can be considered as introduced exotic species (see, e.g., Voeten and Prins 1999),
and resource partitioning with native ungulates would not be expected but, rather, a
certain overlap in resource selection (see Fleischner 1994; Edwards et al. 1996;
Aagesen 2000; Prins 2000). This is the case in North American steppes, where
livestock replaced the bison Bison bison and pronghorn (Schwartz and Ellis 1981;
Hartnett et al. 1997). Thus, dietary niche divergence in sympatric species can occur
even at a very subtle scale (Hartnett et al. 1997). Campos-Arceiz et al. (2004) found
that food overlap between Mongolian gazelles (Procapra gutturosa) and livestock
occurred not only at the main forage categories but also at the selection of plant
parts for foraging.
Interpretation of measures of niche overlap in terms of the implications for
competitive interactions is problematic (Putman 1996). High observed overlap can
imply competition, but only if resources are limited. In fact, observations of high
overlap might equally well be indicative of a lack of competition (see Schoener 1983;
de Boer and Prins 1990; Putman 1996).
The implications these results may have on the Iberian ibex viability and
expansion can be evaluated from different views. Ibex populations in the study
region seem to be in expansion, particularly in the provinces of Albacete, Cuenca
and Guadalajara, if we compare current abundance of the species (Fig. 1) and that of
former studies (e.g., Pe
´rez et al. 2002). Therefore, currently isolated populations
might enter into contact. This may imply new viability risks associated to the in-
crease of certain diseases, such as sarcoptic mange. This disease has already been
detected sporadically in Albacete province (C. Gorta
´zar Unpublished data), so that
a consequent generalisation of its prevalence might occur in the near future. Finally,
hunting pressure on the Iberian ibex is negligible in Castile–La Mancha: a 0.0004%
(63 individuals) of total big game hunted in 1999–2003 period (Garrido 2004).
Therefore, we believe that game activity is not currently disturbing the Iberian ibex
expansion movements in the region.
As a conclusion, we encourage comparative studies of habitat use with other
ungulate species in sympatry (including exotics), as well as a monitoring of disease
prevalence and colonisation process in order to assure the establishment of the
species in central Spain.
Acknowledgements We are grateful to Leticia Dı
´az for her useful comments on a previous version
of the manuscript as well as her advise on the statistical analyses. Two anonymous referees also
contributed to the improvement of the manuscript. We are also indebted to M. Martı
´nez, V. Alzaga,
J. Milla
´n, A. Pe
´rez and J. Vicente for assistance in the field. This research was supported by a JCCM-
CAMA agreement. Pde Asturias and CSIC. J.C. is currently supported by the Ministerio de
Educacio
´n y Ciencia and CSIC through a Ramo
´n y Cajal contract.
3372 Biodivers Conserv (2007) 16:3361–3376
123
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... The common situation reported in most studies, however, is that one or several domestic species strongly outnumber the wild ungulates (e.g. Putman, 1986a, b; Martín Bellido, 2001; Fankhauser, 2004; Acevedo et al., 2007; Fankhauser et al., 2008) and thus have a more signifi cant infl uence. As, in addition, domestic cattle are frequently involved; the domestic species is usually also superior in body size. ...
... We may thus anticipate that competitive effects observed may be asymmetrical, with a greater infl uence of the domestic livestock on the ecological dynamics of the wild population. This is apparent in many examples cited, in that only the wild species adjust habitat use or feeding behaviour , while the domestic species remain indifferent to their wild counterparts (e.g. Acevedo et al., 2007). Such interaction between native species and domestic stock is, further, not a simple, universal phenomenon but is quite clearly structured: cattle and horses, as preferential grazers, tend to show highest overlap and thus potential for competition with native species reliant on a bulk-feeding strategy (sensu Hofmann 1973 Hofmann , 1985); competition for specialist browsers may be afforded by goats, while sheep are most likely to show high overlap with intermediate feeders. ...
... Granados et al., 1998; Palomares and RuizMartínez, 1993; Lasso De La Vega, 1994; Pérez et al., 1994; Gortazar et al., 2000). Acevedo and Cassinello (2009) report that one of the main threats to conservation of this species is the increasing presence of domestic livestock, which can compete for resources (e.g. Acevedo et al., 2007) and transmit diseases to wild ungulates (see examples in Gortázar et al., 2006). Indeed, much of the range of this species, especially in summer months when exploiting the summer high mountain pastures, is shared with sheep, domestic goats, cattle and horses. ...
... The newly occupied areas include the mountains of Central Iberia, the mountains of the peri- Mediterranean arc, and the South bank of the Ebro River (Acevedo and Cassinello, 2009). Habitat preferences of the Iberian wild goat include Holm oak (Quercus ilex L.) forests, pine (Pinus sp.) forests, broom (Cytisus sp.) scrublands, and the presence of rocky outcrops and cliffs is essential (Acevedo and Cassinello, 2009; Acevedo et al., 2007a Acevedo et al., , 2007b Alados, 1985; Esc os and Alados, 1992a Alados, , 1992b Gonzales, 1982). In the Middle Ebro Valley (MEV), Spain, however, are few mountain formations, few rocky areas and steppe vegetation is predominant, and there are few forests. ...
... In our study, the estimated dispersal distance was <5953 m and, although to our knowledge there are no published accounts of the dispersal of the species, some demographic studies suggest that dispersal process occurs within short distances (Fandos et al., 2010). In our study and others (Acevedo et al., 2007a), slope-related variables explained a significant amount of the variation in the distribution of Iberian wild goat which is typical of Caprinae species (Shackleton, 1997). Iberain wild goat use cliffs as a refuge from predators; their short, strong legs and adaptations for these areas allow them to avoid predators. ...
... obs.). Although other studies have reported that elevation had a significant effect on the distribution of Iberian wild goat (Acevedo and Cassinello, 2009; Acevedo et al., 2007a Acevedo et al., , 2007b Acevedo and Real, 2011), in the MEV, that was not the case. Several factors might have been responsible for that difference. ...
... In the cold deserts of the trans-Himalayas, domestic sheep and goats impose resource limitations for the Himalayan ibex (Capra sibirica), leading to an exclusion of the native ungulate from its optimal habitat [2]. The Iberian ibex (Capra pyrenaica) was also displaced to suboptimal habitats in the presence of extensive goat livestock in central Spain [3]. In the Italian Alps, the Alpine chamois (Rupicapra rupicapra) has moved upslope into an entirely novel altitudinal range in the presence of domestic sheep, with an almost 50% decrease in the availability of suitable foraging habitat as a consequence [4]. ...
... Hence, it is difficult to evaluate any consequences of the moderate diet overlap on competitive interactions between the Walia ibex and domestic goat. Nevertheless, given the documented overlap in dietary preferences and the potentially devastating effect of domestic goat on plant diversity [3,5,6,12], the Walia ibex may be highly vulnerable to further increases in goat numbers in the Simen Mountains National Park. This could be enhanced by an additional shift in animal husbandry from cattle to goats, which has been predicted in Africa [71]. ...
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... The presence of livestock usually has a negati� ve effect on their relative abundance and distribution. Livestock act as a disturbance, and ibex retreat to less suitable habitats (Namgail, 2006; Pelayo et al., 2007). The behavioural responses are key to understanding animal–habitat interactions; the way individuals obtain food, seek shelter, escape from predators, find mates, and care for the young can provide clues to the effect of disturbances (Hickman et al., 1993). ...
... 1), may have contri� buted to displacement of walia ibex to the east and to the highest, steepest areas of the park (Hurni & Ludi, 2000). Our study was not designed to determine the relative �uality of habitats for walia ibex, but we encourage biologists to consider the possibility that presence of livestock in former ibex range within the park has forced walia ibex to select habitats of lesser �uality (Pelayo et al., 2007). We concur with, 2003). ...
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... At the beginning of the twentieth century, however, a number of conservation programs helped Iberian ibex populations begin to recover [12], [24], [25]. Currently, the two persisting subspecies are both recovering and expanding [26], with C. p. hispanica today more widely distributed than C. p. victoriae, whose populations are fewer and smaller in extent [14]. Recently a new population of C. p. victoria has been established in Portugal [27]. ...
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