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Predicting the implications of conservation management: a territorial occupancy model of Bonelli’s eagle in Murcia, Spain.

Abstract Bonelli’s eagle Hieraaetus fasciatus is a for the species.

The model, which assumes demographic stability, estimates an equilibrium proportion of habitat threatened cliC-nesting raptor mainly distributed in the coastal regions of the Mediterranean.

The European occupancy as a function of life history parameters, dispersal behaviour and habitat suitability. In spite of population has declined and the species is considered
Vulnerable in Spain.

Before eCective conservation prosome limitations the model identified the most important conservation measures required for an increase in the grammes can be proposed the causes of this decline need to be considered.

In a monitoring programme of the proportion of territories occupied: the improvement of the survival of both territorial and non-territorial birds, population of Bonelli’s eagle in Murcia carried out since 1983 we observed a marked decline, followed by a period and an increase in the proportion of suitable habitat. of stability that began in 1990.

Using demographic data (territorial bird survival, non-territorial bird survival, Keywords Bonelli’s eagle, demography, Hieraaetus fasciatus, management, Mediterranean, Spain, survival, and fecundity) for 1990-1998 we applied a territorial occupancy model to evaluate management alternatives territorial occupancy model. theoretical models available for predicting the probability Introduction that a small population will become extinct and the time that it will take to do so (e.g. Hanski et al., 1996; Hanski, With species facing demographic and habitat pressure it has become increasingly important to quantify the 1999). Lande (1987) adapted the metapopulation model of Levins (1969) to territorial populations in a random extinction risk faced by particular populations (Sutherland, 1998), thus providing objective criteria for determining landscape to evaluate habitat occupancy and extinction thresholds under diCerent management actions.

Lande’s whether or not management intervention is required to ensure long-term persistence. It is known that smaller model describes changes in occupancy rate, as determined by the rates of local extinction and colonization, at populations are more susceptible to extinction (SimberloC 1988), although in general a greater understanding of the a scale of individual territories. This territorial occupancy model becomes particularly useful when the overall relationship between population size and the likelihood of extinction is needed in conservation biology.

In this population viability is more dependent on withinpopulation dynamics (birth rates and death rates) than context the usefulness of modelling for the management of exploited or rare populations has been recognized on between-population dynamics (patch extinction and colonization rates) (Noon & McKelvey, 1996). With (ShaCer, 1981; Silvert, 1989), and there are several regards to management planning, the model could beused to predict the consequences of habitat destruction

Martina Carrete1 (Corresponding author)
Departamento de Ecología e or improvement on the population size of rare or Hidrología, Universidad de Murcia, Campus de Espinardo, 30100, Murcia, Spain. endangered territorial species.

Lande’s model has beenused, for example, to illustrate how habitat fragmentation Jose´ A. Sánchez-Zapata Departamento de Biologý´a Aplicada, Área de Ecología, Universidad Miguel Hernández, Ctra Beniel km 3.2, Orihuela.

would aCect the northern spotted owl Strix occidentalis Alicante, Spain. caurina (Lande, 1988; Noon & McKelvey, 1996).
A number of raptors are included in the IUCN Red Jose´ E. Martý´nez Departamento de Ecologý´a e Hidrologý´a, Universidad
de Murcia, Campus de Espinardo, 30100, Murcia, Spain.

List (Birdlife International, 2000; Hilton-Taylor, 2000) and by far the greatest threat to these species is habitat loss Jose´ F. Calvo Departamento de Ecologý´a e Hidrologý´a, Universidad de Murcia, Campus de Espinardo, 30100, Murcia, Spain. and degradation, followed by interaction with other native species, accidental mortality and the eCect of invasive 1Present address: Departamento de Biología Aplicada, Área de Ecology a, species (Criado & Stattersfield, 2001). Although Bonelli’s Universidad Miguel Herna´ ndez, Ctra Beniel km 3.2, Orihuela, Alicante,
Spain.
E-mail: eco3@um.es

eagle Hieraaetus fasciatus is not globally threatened, it has been included in the Spanish Vertebrate
Red Received 26 March 2001.
Revision requested 10 September 2001.
Accepted 24 May 2002.

Data Book as Vulnerable (Blanco & Gonza´lez, 1992) and 349
© 2002 FFI, Oryx, 36(4), 349-356 DOI: 10.1017/S0030605302000698
Printed in the United Kingdom 350 M.

Carrete et al. has been listed as an Endangered European raptor located by observing territorial activity, courtship, broodrearing activity, the presence of young, and any other (Rocamora, 1994). It is a cliC-nesting raptor found mainly
in Mediterranean countries (Cramp & Simmons, 1980; conspicuous field signs (Fuller & Mosher, 1981).

The population was considered to be organized into del Hoyo et al., 1994), and its main European population,
in Spain, has declined by 25% over the last two decades three stage classes: fledging birds, non-territorial birds
( juvenile, subadult, and adult birds that did not have a (Sa´nchez-Zapata, 1997). The numerous studies of this
species have been concerned with diet (Cheylan, 1981; territory) and territorial birds (individuals occupying a
breeding site, mainly adults). The annual survival rate Real, 1991; Martý´nez et al., 1994; Gil-Sa´nchez et al., 1994;
Ontiveros & Pleguezuelos, 1999), habitat requirements st of territorial birds was calculated as the proportion
of birds present in the population at the start of the (Gil-Sánchez et al., 1996; Ontiveros, 1999; Sánchez-Zapata, 1999) and competition with other cliC-nesting breeding season that was still present in the population at the start of the following breeding season. A bird was raptors (Jordano, 1981; Donázar et al., 1989; Fernández & Insausti, 1990; Gil-Sánchez, 1999). Causes that may considered to be dead if it had disappeared from its breeding site from one year to the next or if it had been lead to territorial desertion have been analyzed, and conservation strategies have been proposed (Real, 1991; replaced by another bird. DiCerential plumage colour during the first 4 years of life allows assessment of the Ontiveros, 1999).

However, little is known about the life history parameters of Bonelli’s eagle and the relative rate of replacement of adults by birds younger than 4 years (Parellada, 1984), which provided us with the influence of these parameters on population trends and the threat of extinction. Such information is vital for maximum territorial survival rate (Real & Man˜ osa, 1997).

The absence of observations of a bird and of arranged designing and evaluating conservation plans.
We have used the territorial occupancy model (Lande, nests and droppings on perches was taken as evidence
of the disappearance of a pair. When only one bird 1987) to identify the most appropriate management strategies for Bonelli’s eagle. The aims of this paper are was observed in a breeding territory, the loss of half a pair was recorded. When a pair was not recorded to model the proportion of suitable habitat occupied by the species as a function of the available habitat and the in its traditional site, we searched within a radius of several km for suitable breeding habitats, to exclude the life history parameters of individuals, and to predict and discuss the value of diCerent conservation strategies possibility that the pair had moved to a new breeding site. for the species.

We assume that the region is made up of a number of territories H, a proportion h of which are suitable for Study area Bonelli’s eagle.

The territorial occupancy model (for a detailed description see Appendix) uses the proportion The study area is the province of Murcia in southeast Spain, an area of 11,317 km2 with a semi-arid p of suitable territories occupied by females at demographic equilibrium (i.e. when the population size and Mediterranean climate, crossed by mountains that reach 2,000 m. The vegetation is typically composed of shrubs, age structure are constant) and h to estimate the ‘demographic potential’ k of the population. The demographic grasslands and mixed forest, interspersed with cultivated lands (Carrete et al., 2000).

Bonelli’s eagle uses cliCs for potential gives the equilibrium proportion of territories that would be occupied by females in a completely nesting, although in other regions its nests have been observed in trees (L. Palma, pers. comm.). Its home suitable region, and it is determined by the life history parameters and dispersal behaviour of the species range includes open landscapes, where it obtains its food (Carrete, 2002). Although Murcia held one of the (Lande, 1987). The model allows us to predict the eCects of environmental and demographic fluctuations (changes highest densities of Bonelli’s eagle in the 1980s, the species has since declined considerably because of direct in h and k, respectively) on the proportion of suitable territories occupied by females. persecution, electrocution by and collision with power lines, and the pressure of recreational activities such as We obtained k from estimates of p and h, and using this value and demographic data we calculated the cycling and climbing (Sa´nchez-Zapata, 1997; Real et al.,
2001). search ability m (equation 4, Appendix), which is the
mean number of searches that non-territorial birds are
able to make for a suitable unoccupied territory before Methods perishing of starvation or predation. The proportion h
of the region that is suitable for Bonelli’s eagle was We studied the long-term changes in this population of
Bonelli’s eagle from 1983 to 1998. Known territories and determined from the number of territories occupied by
the species during the period when the population was potential breeding habitat for the species were visited
during the breeding season. Breeding territories were relatively stable, i.e. 1990-1998, and the total number of
© 2002 FFI, Oryx, 36(4), 349-356

351 Territorial model of Bonelli’s eagle territories H known for cliC-nesting eagles (Bonelli’s study area held 42 breeding pairs (Sa´nchez-Zapata, 1997) but during the 1980s many territories were abandoned, eagle and golden eagle Aquila chrysaetos, combined) in Murcia (120 territories, Sa´nchez-Zapata et al. 2000).

The mainly because of direct persecution, and today only 26 of these areas could be considered suitable for number of territories suitable for the species that were occupied during the year 1998 as a proportion of the the species. Golden eagles have colonized eight of the abandoned territories, and in the other eight territories total number of territories in the region available during the period 1990-1998 was used as a measure of p, the direct persecution could still be taking place. Table 1 summarizes demographic and other parameters for the proportion of suitable territories occupied by females at demographic equilibrium. period 1990-1998.

The relationship between p and h is shown in For fledging survival rate so we used 0.78 (Real & Man˜ osa, 1997).

Productivity P was calculated as the Fig. 2. When h increases, p increases until a value, k, that represents the equilibrium proportion of territories number of young fledged per territorial pair. Demographic
analyses are usually formulated exclusively in that would be occupied in a completely suitable habitat
(h=1).

A decrease in the proportion of suitable territories terms of females and therefore, assuming a 1 : 1 sex ratio
(Real & Man˜ osa, 1997), the number of female oCspring lowers the equilibrium occupancy rate, with a steep
decline as the proportion of suitable habitat declines. of a female per year b was calculated as P/2. The
survival rate sn of non-territorial birds was obtained by The demographic potential estimated for the species
in Murcia is k=0.93 and the minimum proportion of equating it with the probability of successful juvenile
dispersal (equation 2, Appendix) (Noon & McKelvey, suitable habitat at which the population would become
extinct (the extraction threshold, p=0) is 1-k=0.07 1996).
We used the model to examine the relationship (8 territories). We estimated the minimum search ability,
m, to be 3.7. between p and h, and the eCect of changes in demographic parameters on p and on the relationship between The equilibrium occupancy of suitable habitat by
females p responds in diCerent ways to changes in p and h.
fecundity b, fledgling survivorship so , search ability m,
and annual survival rate of territorial birds st (Fig. 3).

Results Considering only the most likely ranges of these parameters for Bonelli’s eagle (Real & Man˜ osa, 1997) we We surveyed a total of 112 known territories of cliCnesting
eagles in Murcia, i.e. areas with cliCs that hold found that st had the strongest influence on p (Fig. 3a),
followed by m and b (Fig. 3b and c, respectively). nests constructed by golden or Bonelli’s eagles.

The Bonelli’s eagle population of Murcia declined from 35 Fledgling survivorship so , did not seem to influence p
to any great extent (Fig. 3d). breeding pairs in 1983 to 18 in 1990, since when they appear to have stabilised (Fig. 1). During the 1970s the Using the highest values recorded in the literature (Arroyo & Garza, 1995; Real & Man˜ osa, 1997) for the Table 1 Estimates of demographic statistics, habitat variables, and the demographic potential’ and extinction threshold (in terms of number of territories) of Bonelli’s eagle in Murcia over 1990-1998 (see text and Appendix for details).

Parameter Value
Probability of survival of fledglings so 0.78
Probability of survival of non-territorial 0.24
birds sn Probability of annual survival of territorial 0.89
birds st No. female oCspring per year b 0.59
Mean lifetime production of female oCspring 4.18
by a female R80

Potential habitat H, i.e. number of territories 112
Proportion of habitat suitable h 0.23 (26)
(number of territories)
Proportion of habitat occupied p 0.69 (18)
(number of territories)
Number of occupied territories
Demographic potential k±s2 0.93±0.02
Fig. 1 The number of territories occupied by Bonelli’s eagle Extinction threshold 1-k (number of territories) 0.07 (8)
Hieraaetus fasciatus from 1983 to 1998 in Murcia, south-east Spain.
© 2002 FFI, Oryx, 36(4), 349-356
352 M. Carrete et al.

likely outcomes of management strategies that focus on
improvement of habitat availability and ‘improvement’
of these demographic parameters.
If the proportion of suitable habitat is increased,
the proportion of territories occupied increases up to a
maximum known as the ‘demographic potential’. Because
the model considers proportions, increments in suitable
habitat are always matched by a greater number of
breeding pairs. To increase the amount of suitable habitat,
factors related to territorial desertion should be taken
into account. Mortality is the most important cause of
abandonment of territories by Bonelli’s eagle in Murcia,
but the situation is complex because direct persecution,
habitat quality and competition with golden eagles may
all be involved. Habitat quality plays a role because
when prey (mainly rabbits Oryctolagus cunniculus) availability
is low Bonelli’s eagle may feed on pigeons, and
breeding pairs may be persecuted by pigeon fanciers.
The absence of a pair of Bonelli’s eagles from a territory
is then exploited by golden eagles, and whilst this
species may not be responsible for displacement, it may
Value in Murcia be preventing recolonization. In this way, controls and Fig.

2 Changes in the proportion of territories p occupied by
actions to prevent conflicts between eagles and people females at demographic equilibrium as a function of the proportion 1of territories h that are suitable. The extinction threshold at p=0, may increase habitat availability if applied in areas the demographic potential’ k at h=1, and the values of h and p in where direct persecution is still active (Carrete et al., Murcia are indicated (see text and Table 1 for details). 2002). Although Bonelli’s eagle seems to be tolerant of habitat transformation such as increases in irrigated and urban lands, it is important that there are no increases in such landscape components around breeding areas fecundity and survival rate for territorial birds (b=0.62 and st=0.96, respectively) and the optimum values because in other regions habitat degradation is known
to be a major problem for the species (Arroyo & Garza, obtained with the model for search ability and survival
rate of fledglings (m=7 and so=0.83, respectively) 1995).

Even if the improvement in adult and nonterritorial
bird survivorship is the most important demo- we can see how the equilibrium occupancy of suitable habitat changes with the proportion of the region that graphic conservation action for the species, providing breeding area for birds that are searching for territories is suitable (Fig. 4) under diCerent management options.

Increasing the proportion of suitable habitat, h, increases would increase the breeding population size. This is
particularly important if we consider that the species the number of breeding pairs. However, for the same
quantity of suitable habitat h, the proportion of occu- has a high value of the demographic potential k, i.e. it
tends to occupy a high proportion of the available pancy p expected is higher when the survival rate of
territorial birds st increases. Management actions focused habitat.

Changes in life-history parameters influence the per- on improving m would also increase p, although not to
the same extent as increases in st . Increases in b and so sistence of a population by means of the demographic
potential. Increases in the survival rates of territorial have a lesser eCect on p. and non-territorial birds, st and sn, had the greatest eCect on the demographic potential, while fecundity b and fledgling survivorship so had lesser eCects. Adult survival Discussion is one of the most important factors influencing the population growth rate of other long-lived birds (Mertz, Lande’s (1987) model is a useful tool to predict how numbers of a breeding population of a territorial species 1971; Newton, 1979; Real & Man˜ osa, 1997). Because reproductive performance of birds, in general, improves may change as a function of the proportion of suitable habitat in a region, h, and life history parameters (adult with age (Forslund & Part, 1995; Pa¨
rt & Forslund, 1996;
Sa´nchez-Zapata et al., 2000), increasing adult survival survivorship st , fledging survivorship so , non-territorial
survivorship sn, and rate of production of female oC- will have an additional benefit on the long-term productivity
of the population (Newton, 1989). The territorial spring b). The model is able to predict, qualitatively, the
© 2002 FFI, Oryx, 36(4), 349-356
353 Territorial model of Bonelli’s eagle

Fig. 3 Relationship between the proportion of suitable territories p occupied by females at demographic equilibrium, i.e. when the
population size and age structure are constant, and (a) territorial bird survivorship st , (b) search ability m, (c) fecundity b, and (d) fledgling
survivorship so .
bird survivorship used in the model, which was a maxi- available habitat occupied p and increasing the proportion
of suitable habitat h by making abandoned mum estimation, was lower than that found in other areas
(Real & Man˜ osa; 1997), and so eCorts could be made to territories more suitable.
The model also predicts that Bonelli’s eagle is improve it. Because direct persecution has been found
to be responsible for territorial abandonment in the relatively sensitive to the search ability of dispersers m,
the mean number of territories that a disperser visits study area (Carrete et al., 2002), increases in vigilance
by forest guards, combined with reintroduction of prey before it dies. High dispersal mortality, mainly caused
by electrocution by and collisions with power lines and such as rabbits, and installation of pigeon cotes to reduce
the predation pressure of eagles on racing pigeons persecution in dispersal areas (Real et al., 2001), results
on average in few territories being searched. This means in areas where conflicts with pigeon fanciers occur
(Sa´nchez-Zapata, 1997), could help to reduce the capture that, although some individuals visit a lot of breeding
areas, a high proportion of disperser do not visit any. and killing of eagles. Such management actions would
have eCects at two levels: increasing the proportion of Despite the importance of a knowledge of movement
© 2002 FFI, Oryx, 36(4), 349-356
354 M. Carrete et al.
areas where the two species are sympatric, interactions
between these species should be taken into account in
conservation programmes.
Lande’s model is too optimistic in several respects
because of the simplifying assumptions made. Alle´e
eCects (the diBculty in finding a mate), edge eCects
(resulting from the finite extent of regions containing
suitable habitat), competition with sympatric species,
and the influence of stochastic fluctuations on life history
parameters may increase the extinction threshold of a
territorial population (Lande, 1987). Therefore, as with
other conservation problems, the results should be applied
only as general guidelines. Practical considerations and
local constraints will govern the best decisions in any
single instance.
The Bonelli’s eagles that we studied are not a discrete
population, but a segment of a much larger one
Fig. 4 Changes in the proportion of suitable territories p occupied (del Hoyo et al., 1994), and birds appear to be move
by females at demographic equilibrium, i.e. when the population between Murcia and the surrounding areas. Thus, the
size and age structure are constant, as a function of the proportion
regulation of local breeding densities may depend not of territories h that are suitable suitable, in response to changes in
only on local events but also on the dispersal of indi- territorial bird survivorship st , search ability m, fledgling
survivorship so , and fecundity b (see text for details). viduals over a wider area. The decline of Bonelli’s eagle
throughout its range requires conservation action and,
to be eCective, these actions need to take place at both patterns (Wiens, 1996), little is known about the dispersal
of most species, and in the case of Bonelli’s eagle, local and regional scales. The stability observed in the
population in Murcia since 1990 has allowed us to apply although young birds have been wing-tagged and ringed
to estimate pre-adult mortality (Real et al., 1996), no Lande’s (1987) territorial occupancy model, which could
be a useful planning tool for management of the species detailed data on dispersal behaviour exists. However,
during dispersal juveniles do leave the breeding in this region. Integrating information from diCerent
populations to obtain a large-scale conservation pro- population in which they were born, and so non-local
conservation measures could improve survival. Our gramme for the species should be the next step in the
conservation of the species. estimation of the survival rate of non-territorial birds
was higher than that obtained previously for the species
in Levante and Catalun˜a in Spain and in southern France
(Real & Man˜ osa, 1997). Although the model cannot Acknowledgements
discriminate which part of non-territorial survival rate
We would like to thank M.A. Sa´nchez, J. Royo, S. Eguý´a, corresponds with local dispersal mortality and which
A. Ortun˜ o, P. Corte´s, A. Gime´nez, Eloy, M. Martý´nez, with movements among neighbouring populations,
I. Paga´n and the personal of the Forestry Guardery for we considered that this value of survival rate is useful
their field assistance. V. Soler reviewed and improved for modelling because, in practice, it is the actual conthe
English version of the article. Hugh Possingham and tribution of dispersing birds to the local population.
an anonymous referee made valuable comments that Productivity of the population in Murcia was similar to
allow us to substantially improve the article. M. Carrete that of other populations (Real & Man˜ osa, 1997), and as
was supported by a predoctoral fellowship of the prey availability does not seem to be limiting repro-
CONICET (Argentina). duction (Ontiveros and Pleguezuelos, 1999; Carrete et al.,
2002), actions to improve it for this reason do not appear
to be necessary at the present time.
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Hanski, I., Moilanen, A. & Gyllenberg, M. (1996) Minimum R.D. Chancellor), pp. 523-528. W.W.G.B.P., Berlin, London
viable population size. The American Naturalist, 147, 527-541. and Paris.
Hilton-Taylor, C. (compiler) 2000 IUCN Red List of Threatened Rocamora, G. (1994) Bonelli’s eagle Hieraaetus fasciatus. In Birds
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Jordano, P. (1981) Relaciones interespecý´ficas y coexistencia M.F. Heath). Birdlife International, Cambridge, UK.
entre el A´
guila real Aquila chrysaetos y el A´ guila perdicera Sa´nchez-Zapata, J.A. (1997) Plan de Recuperacio´n del Aguila
Hieraaetus fasciatus en Sierra Morena Central. Ardeola, 28, perdicera en la Regio´n de Murcia. Ambiental S.L., Consejerý´a
de Agricultura, Agua y Medio Ambiente, Murcia, Spain. 67-88.
© 2002 FFI, Oryx, 36(4), 349-356
356 M. Carrete et al.
Sa´nchez-Zapata, J.A. (1999) Las aves rapaces y su relacio´n con la are independent of age of first reproduction a, then
estructura del paisaje en ambientes mediterra´neos semia´ridos. PhD the mean lifetime production of female oCspring by a
thesis, Universidad de Murcia, Murcia, Spain. female, Ro, is
Sa´nchez-Zapata, J.A., Calvo, J.F., Carrete, M. & Martý´nez, J.E.
(2000) Age and breeding success of a golden eagle (Aquila Ro=sosn . bsx-a
t =sosnb/(1-st ) (1)
chrysaetos) population in SE Spain. Bird Study, 47, 235-237.
where so and sn are fledging and non-territorial ShaCer, M.L. (1981) Minimum population sizes for species
conservation. BioScience, 31, 131-134. survivorship.
Silvert, W. (1989) Modelling for managers. Ecological Modelling, If the probability that an obligately dispersing juvenile,
47, 53-64. as with Bonelli’s eagle (Sa´nchez-Zapata, 1997; Man˜ osa
SimberloC, D. (1988) The contribution of population and et al., 1998), succeeds in finding a suitable unoccupied
community biology to conservation science. Annual Review of
territory in m searches is 1-( ph+1-h)m (Noon and Ecology and Systematics, 19, 473-511.
McKelvey, 1996) when the population is at demographic Sutherland, W.J. (ed.) (1998) Conservation Science and Action.
equilibrium, i.e. with constant population size and age Blackwell Science, Oxford, UK.
Wiens, J.A. (1996) Wildlife in patchy environments: structure, Ro=1 or
metapopulations, mosaics and management. In
[1-(ph+1-h)m]R8o=1 (2) Metapopulations and Wildlife Conservation
(ed. D.R. McCullough), pp. 53-84. Island Press, Washington, where R8o=sob/(1-st ) is the mean lifetime production
D.C., USA.
of female oCspring by a female. Solving equation 2 for
p gives
Biographical sketches
p=G1-(1-k)/h, h>1-k
0, h.1-k
(3)
The authors are studying various aspects of avian biology,
particularly of raptors. Their interests include the factors where
limiting reproduction and survival, competition, habitat
k=[1-1/Ro ]1/m=[1-((1-st)/(sob))]1/m (4) selection processes and dispersal patterns, and the elaboration
of management actions that may ensure the conservation is a measure of the ‘demographic potential’ of the
of the species being studied.
population (Lande, 1987), the equilibrium proportion of
territories that would be occupied by females in a
completely suitable region. When detailed information
on life history parameters is not available k can be Appendix - The territorial occupancy model
calculated directly from p and h as k=1-(1-p)h
(Lande, 1988). The sampling variance of k can be esti- In this model (Lande 1987) we assume that the region
mated as s2
k=h2s2
p , where s2
p=p(1-p)Np and Np is the is made up of territories H, a proportion h of which
number of suitable territories sampled for occupancy. are suitable; p is the proportion of suitable territories
The extinction threshold, hmin=1-k, is the minimum occupied by females at demographic equilibrium. If
proportion of suitable habitat necessary for population we assume that the expected rate of production b of
persistence. female oCspring by a female and adult survivorship st
© 2002 FFI, Oryx, 36(4), 349-356
Oryx Vol 36 No 4 October 2002


Autores:
Martina Carrete, José A. Sánchez-Zapata, José E. Martinez and José F. Calvo.

El Dr. José Antonio Zapata es Biólogo. Y profesor de la Universidad Miguel Hernandez. En Elche. Alicante. España.

Esta documentación fue facilitada a Ibérica 2000 por Vedema. Murcia.
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