Prey and prey-age preference by the Iberian wolf Canis lupus signatus in a multiple-prey ecosystem. Isabel Barja. (2009)

Foto de Javier Muñoz Gutiérrez. En: fotonatura.org/

Abstract

In many regions of the Iberian Peninsula, wild ungulates have disappeared and wolves Canis lupus often depend on garbage dumps and domestic animals. This paper represents an example of wild ungulate preferences of the Iberian wolf Canis lupus signatus in an environment with no human-wildlife conflicts, because wolves rarely predate on livestock. I studied the patterns of prey selection by the Iberian wolf during May 1998-October 2002 in northwestern Spain, in an area which supports a diverse community of wild ungulates and in which also domestic ungulates are present. My analysis of 593 wolf scats showed that wild ungulates were consumed preferentially over other prey (i.e. domestic ungulates, carnivores and lagomorphs). Roe deer Capreolus capreolus was the most important prey species followed by red deer Cervus elaphus and wild boar Sus scrofa. Domestic ungulates were poorly represented in the wolf diet. Predation frequencies of domestic and wild ungulates varied seasonally and between years. The consumption of roe deer and wild boar increased during the birthing season, probably because of the higher vulnerability of newly born animals; wolves predate mainly on juvenile roe deer and wild boar.

Introduction

Most studies on the feeding ecology of the wolf Canis lupus have been conducted in North America. In Europe, there have been various studies on wolf diet, some of which showed wild ungulates as the wolf’s main prey. However, the feeding habits of Iberian wolves Canis lupus signatus have received little attention and the studies performed have shown that the species’ food habits are highly variable depending on the areas in which the species occurs. In many regions of the Iberian Peninsula, domestic ungulates are of importance, whereas in other areas, the most relevant prey is wild ungulates. However, the former studies were fundamentally descriptive, and usually only included data corresponding to one year. It is not known, therefore, whether and how wolf feeding habits change over time. Furthermore, the information contained data, which did not study the age of the selected prey. The trophic ecology of the Iberian wolf, therefore, remains largely unknown. The aim of my study was to test the hypothesis that the Iberian wolf is an opportunist species. To test this hypothesis, I predicted that: 1) the wolf consumes the most abundant prey species and also food which is easier to acquire (i.e. domestic ungulates, carrion and garbage), 2) the consumption of prey species varies throughout the year according to prey vul nerability, so wolves will prey on the individuals and species easier to capture, and 3) for an opportunist species, in a multiple-prey ecosystem and with high food availability, trophic specialisation should not be observed over time.

Material and methods

Figure 1. Location of the study area in the Iberian Peninsula.

My study was conducted in the Macizo Central Ourensano in Galicia (northwestern Spain), a mountainous area that includes the Montes do Invernadeiro Natural Park (Fig. 1). The study area, which covers 120 km2 and is part of a larger continuous area (45,829 km2) […] The human population density in the study area is one of the lowest in the region (0.8 habitants/km2).

Scat analysis and collection

Both prey and prey-age preferences of the Iberian wolf were assessed from scats collected systematically every 45 days during May 1998-October 2002. Scats were collected by surveying roads and firebreaks in the study area. Faecal marking sites (mainly crossroads) were also included in the search, because the probability of defecation in these places is greater. […]The date of collection and age of all scats were registered. Maps with a grid of 1 km2 cells (Universal Transverse Mercator,UTM) were used to record the scat position. […] Analysis of scats followed standard procedures. […]

Prey and biomass estimation

The linear regression model used for ingested prey was y=0.0731+0.00406x (R2=0.84, F=42.4, df=1,8, P=0.0002; derived from Table 1 in Ruehe et al. 2003), where y is the biomass ingested (in kg) per collected scat, and x the average consumed mass (in kg)of an individual of each prey type.

To estimate the ingested biomass of domestic and wild ungulates (i.e. roe deer Capreolus capreolus, red deer Cervus elaphus, wild boar, sheep Ovis aries and goat Capra aegagrus), the relative proportions of the two age classes ( juvenile and adult) were taken into account (Table 1). However, to calculate the ingested biomass of fallow deer Dama dama and mouflon Ovis orientalis, the average mass for the two age classes was used, because it was impossible to assess the relative age of the consumed individuals. For carnivores and lagomorphs, the ingested biomass was calculated considering only the mass of adults.

To determine the densities of wild ungulates (i.e. roe deer, red deer and wild boar) in the study area, observations of all species were registered along four transects whose total length was 82 km. […] Goats and sheep are maintained in an intensive system (700 individuals) in the study area, where as cows Bos Taurus and horses Equus caballus are in an extensive system (86 individuals). All domestic and wild ungulates were potentially available to wolves all year around.

Table 1. Composition of Iberian wolf diet during May 1998 - October 2002 based on 508 scats. The ingested biomass (a in kg) was calculated using body masses only for adults. The birds (b) were not included in the linear regression model, because only mammals
were included in the feeding trials. These results were estimated on the basis of the consumed prey mass of an individual prey, which represents x in the biomass equation. The prey mean mass (c in kg) was obtained from Urios 1995, Llaneza et al. 1996, Blanco 1998 and Mateos-Quesada 2002.

Data analysis

I used a hierarchical log-linear analysis (Backward method) to investigate the effects of season and year simultaneously on the consumption of domestic and wild ungulates. […]

Figure 2. Percentage (frequency of occurrence) of two domestic
and three wild ungulate species in the Iberian wolf diet per year.
The Shannon diversity index (H') and dominance index (D) are
calculated per year. In 1998: N=74, in 1999: N=146, in 2000:
N=96, 2001: N=78 and in 2002: N=94.

Results

General remarks

A total of 593 scats were used for dietary analysis. A fraction (10.9%) of the scats consisted of a combination of soil, plants and undetermined matter; 6.2% of the scats contained soil and 9.4% contained B. sylvaticum, but none of these items were considered to be food. The majority (98.5%) of the analysed scats contained remains of just one prey species, and only 1.5% contained remains of two prey species. Prey species were identified in 87.3% of the scats collected. In terms of biomass, the types of food identified in the analysed scats were wild ungulates (87.1% including roe deer, wild boar, red deer, fallow deer and mouflon), domestic ungulates (11.3% including goat and sheep), carnivores (1.1% including dog Canis familiaris, cat Felis catus and badger Meles meles) and lagomorphs (0.5% rabbit Oryctolagus cuniculus). […]

Figure 3. Percentage (frequency of occurrence) of two domestic
and three wild ungulate species consumed per season. The percentage
of occurrence for each prey species is based on the total
number of scats found per season.

Annual and seasonal patterns

Roe deer was the main prey taken in all years (Fig. 2). In 2001, the lowest dietary diversity and the highest dominance were found, taking into account the following prey species: roe deer, red deer, wild boar, goat and sheep. The highest diversity and the lowest dominance values corresponded to 1998 (see Fig. 2). Roe deer was the prey species that was consumed most often in all seasons (Fig. 3), but especially during summer (52.0%; frequency of occurrence) and spring (26.2%). The consumption of wild boar was greater in spring (37.1%) and autumn (31.0%) than in summer (19.8%) and winter (12.1%). The highest consumption of red deer occurred in spring (37.4%), followed by autumn (28.1%), winter (26.9%) and summer (7.6%). The consumption of domestic ungulates (sheep and goats) also showed seasonal variation, with consumption significantly higher in spring (50.0%) and summer (23.8%) than during autumn and winter. […]

Prey-age preferences

Analysis of bone remains allowed the identification of prey species in 85 of the 119 scats in which they were found. Of the scats, 69.4% contained bone remains of roe deer, while 27.0% contained wild boar bones, 2.4% goat/sheep bones and 1.2% red deer bones. Wolves selected juveniles from roe deer and wild boar populations: 74.1% of roe deer and 82.6% of wild boar whose age was determined were juveniles (<1 year old).

Discussion

The wolves studied fed mainly on wild ungulates, while domestic ungulates and other preys (carnivores, lagomorphs and birds) were taken occasionally. In my study, the consumption rate of wild and domestic ungulates did not depend on their availability. […]The presence of livestock remains in wolf scats implies scavenging behaviour, because no attacks on livestock were reported during my study. Furthermore, in a zone of the study area (Montes do Invernadeiro Natural Park), horses and cows were kept in an extensive system, but there was no indication that wolves preyed on them (neither on adults nor on young). […]

The scarce consumption of livestock species in the study area could be correlated with the high abundance, richness and diversity of wild ungulates […] However, predation on domestic ungulates may remain high if livestock is locally abundant and the methods of livestock raising are inappropriate, i.e. the livestock is left unguarded in the countryside. In some regions of the Iberian Peninsula with high human population densities and scarce wild preys, wolves take livestock, carrion and even garbage […]

Conclusions

The trophic position of the wolf in the study area is closer to a facultative specialist than to an opportunist species, because a facultative specialist may change from a key food item when other profitable prey is available. Furthermore, it is important to emphasise that the predation upon roe deer in the study area could depend on local feeding specialisation of the studied wolves.

The study of wolf populations inhabiting areas which are only a little altered by men, and with a high availability of wild ungulates and low human population densities, provides very valuable information on the wolf diet under conditions of low human interference. Understanding the factors related to wolf prey preferences in areas where different potential prey species coexist is of great use in reducing the number of attacks on livestock. In areas with low wild ungulate densities, and where wolves therefore prey on domestic ungulates, reinforcement of wild prey numbers, surveillance of livestock and limitation of the access to carrion would force wolves to specialise in the consumption of wild prey and to transmit this behaviour to their offspring. This would help minimise the conflicts between wolves and humans, which without doubt would help to guarantee the long-term conservation of the species.

Prey and prey-age preference by the Iberian wolf Canis lupus signatus in a multiple-prey ecosystem. Isabel Barja. (2009)  http://bit.ly/PI5wja Wildl. Biol. 15: 147-154 (2009) (Publicado en internet por http://www.wildlifebiology.com/ )

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Isabel Barja en RTVE

El lobo ibérico prefiere los animales salvajes a las ovejas

• El lobo ibérico prefiere los animales salvajes a las ovejas
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  Una interesante entrevista a Isabel Barja (1/11/2009) en el periódico La Región: "El lobo, a pesar de su mala prensa, no busca en las granjas su principal alimento": Entrevista

Conservation and control strategies for the wolf (Canis lupus) in western Europe based on demographic models: Guillaume Chapron et al. (2003)

Abstract
Securing the long-term acceptance of large carnivores such as the wolf (Canis lupus) in Europe and North America raises a difficult challenge to conservation biologists: planning removals to reduce depredations on livestock while ensuring population viability. We use stochastic-stage-structured population models to investigate wolf population dynamics and to assess alternative management strategies. Among the various management strategies advocated by agencies, zoning that involves eliminating wolves outside a restricted area should be designed with caution, because probabilities of extinction are extremely sensitive to the maximum number of packs that a zone can support and to slight changes in stage specific survival probabilities. In a zoned population, viability is enhanced more by decreasing mortality rates in all classes than by increasing wolf zone size. An alternative to zoning is adaptive management, where there is no limit on pack number but population control can be operated whenever some predefined demographic conditions are met. It turns out that an adaptive management strategy that removes a moderate percentage (10%) of the population following each year of more than 5% of total population growth would provide visible actions addressing public concerns while keeping extinction probability low.

Introduction
Conflicts with human populations remain the major threat to carnivore persistence. Carnivore may kill domestic and game animals as well as threaten humans and, as a consequence, many carnivore species have been facing widespread persecution. Protected
areas often offer insufficient protection, as they may be too small to encompass full home ranges, and substantial mortality is caused by contact with people at reserve borders. Large carnivore conservation may be successful in the long term only if people can accept free ranging predators in their area. This can be achieved if adequate conservation strategies maintaining viable populations while allowing removal of individuals are implemented.
Focusing on the recent expansion of the wolf Canis lupus in Western Europe, this paper addresses thedual nature of the conservation problem raised by large carnivores: regulating the population to address public concern, while maximizing population viability. [...]

[...] In this paper, we develop stochastic models to study the dynamics of a recolonizing wolf population and compare several management strategies, with an emphasis on the wolf population in the Western Alps. We model a zoning strategy where wolves are tolerated in a restricted area only, and an adaptive management strategy where some wolves are removed whenever the annual population growth rate reaches a given threshold. We examine whether such strategies would make it possible to maintain a viable population while allowing for population control to minimize depredation on livestock. [...]

Methods

Pack of wolves with Alpha chief (first)

Wolf biology
The unit of a wolf population is the pack, consisting of a breeding pair and their offspring (from one or more generations). The dominant adult female in each pack breeds every year, usually producing a single litter. Subordinates rarely become dominant in their natal pack. Pups reach their adult size by winter, and most of them disperse as yearlings. A dispersing wolf may colonize a vacant territory, or it may join another pack and replace a missing breeding member. When both breeding adults die, the pack usually disintegrates, leaving the territory vacant and creating an opportunity for recolonization.Wolves are not habitat-specific and can live wherever they have sufficient food resources and are tolerated by humans. There is no simple relationship between human density and wolf persistence in a given area. [...]
 

Life cycle modelling
All our population projections involve the same sequence of events. (i) Winter mortality affects the whole population and accounts for annual mortality. (ii) Dispersal of subordinates is conditional to the survival of the breeding pair: if the breeding pair disappears (both partners die), remaining pack members disperse, but if at least one breeder survives, subordinates disperse with some probability specific to their class. (iii) Dispersing wolves search for a vacant territory and a partner. We neglect the probability that a dispersing wolf joins an extant pack where no breeder is missing. (iv) Reproduction takes place in spring if
a breeding pair is present. Age at first reproduction is always 22 months (dispersing juveniles must wait one year before looking for a mate). Only one litter is produced per year. (v) Pup mortality takes place in summer and accounts for infectious diseases that are often deadly for pups. In autumn, the distributon of wolves in the population is censused and then updated according to the following scheme (see also Fig. 1).

Fig. 1. Life cycle graph for a wolf stage-structured population. P: Pups, J: Juveniles, S: Subadults, Di: Dispersers, A: Adults, Do: Dominants. All stages are in packs except dispersers. See text for arrow details.

1. Surviving pups become juveniles.
2. Surviving juveniles that have not dispersed become subadults.
3. Surviving juveniles that have dispersed become dispersing wolves.
4. Surviving subadults that have not dispersed become adults.
5. Surviving subadults that have dispersed and found a territory and a mate become pack breeders.
6. Surviving adults that have not dispersed remain in the adult class.
7. Surviving adults that have dispersed and found a territory and a mate become pack breeders.
8. Dispersing wolves that found a territory and a mate become pack breeders.
9. Surviving pack breeders keep the same status.
10. Surviving pack breeders give birth to pups. [...]

Spatial structure
Subordinate dispersal probabilities are not equal between packs as they depend upon the actual survival of pack leaders. Therefore, our model describes explicitly the spatial arrangement of territories and individual movements between them. We assume that any territory may be either empty, or occupied by one pack. We fix the environment carrying capacity to K = 20 territories. One pack can occupy only one territory and this induces a ceiling-type density dependence on pack numbers. [...]

Stochastic simulations
Reproduction occurs in territories containing a male and a female breeder. Survival and fecundity are treated as binomial and Poisson variates, respectively. Our Monte Carlo simulations involve 250 runs each. We tested on a restricted number of simulations that a higher number of runs did not change result precision. A population qualifies as extinct once all classes are empty. [...]

Discussion
Our analysis shows that a wolf population has a high potential growth rate under favourable ecological conditions, but can decline dramatically in response to reduced survival. The wolf is a species sensitive to high killing rates, as exemplified by its eradication from many areas, in contrast with smaller, more versatile species such as the red fox (Vulpes vulpes). However, the wolf shows a strong ability for recolonization once persecutions are stopped. Maximum annual growth rates obtained from field studies can reach 43%. [...]

Fig. 3a. Extinction probabilities as a function of changes of parameters
under median scenario S2.

[...] Population growth is more sensitive to the survival probability of dominants (Fig. 3a). This result is not surprising, because wolf complex social structure results in a lower number of reproductive units in the population compared to other solitary species, thereby implying a high sensitivity to the survival of breeders. [...] 
[...] Our study is aimed at identifying management strategies to help maintaining a viable population while allowing for population control to reduce depredations on livestock. One important conclusion is that viability thresholds under a zoning strategy are extremely sensitive to the number of packs and to slight changes in demographic parameters. In particular, population viability critically relies on securing a sufficient number of packs in the wolf zone while keeping their mortality rates as low as possible. As a consequence, for a population under or at its zoned viability threshold, the removal of wolves should be firmly discouraged. Although zoning strategies are likely to be implemented in the future for wolves in western Europe, such strategies should be considered carefully and implemented only when enough demographic data are available, so that reliable estimates of population size and parameters are available. [...]

Fig. 4. Extinction probabilities as a function of initial population
size (in packs). Carrying capacity is 20 packs.

[...] The question of wolf management has become a public and political matter in countries (including France, Norway, Sweden, Switzerland, and USA), where previously extirpated wolf populations are now roaring back, inflicting damages to cattle farming activities that have lost the tradition to cope with large carnivores. [...] 

Fig. 5. Extinction probabilities calculated when population (in
packs) is prevented for exceeding its initial size. This corresponds
to a zoning management strategy.

[...] Focusing on an absolute number of packs that would secure the viability of the Alpine wolf population remains hazardous given the current uncertainty on population size and parameters. We would only suggest that no zoning should occur before the population reaches more than 12 packs (Fig. 5). Our simulations suggest that it should nonetheless be possible to implement a moderate number of wolf removals following years of moderate or large population growth. [...]
[...] Our study has broader implications for the management of social carnivores. An important conclusion of our model is that the difference between a viable and unviable population takes place over a short parameter space (Figs. 4 and 5). [...]
[...] One more general conclusion of our modelling exercise is that the control of population or the design of reserves, particularly for social species where the parameter space between viability and decline is reduced, requires the development of species-specific demographic models. Indeed, the social structure of the species needs to be fully explicit in the life cycle graph. This can be achieved by incorporating classes of social status rather than age classes, with probabilistic transitions between them.

Conservation and control strategies for the wolf (Canis lupus) in western Europe based on demographic models. Guillaume Chapron, Stéphane Legendre, Régis Ferrière, Jean Clobert, Robert G. Haight. Comptes Rendus Biologies (CR BIOL) 326 (2003) http://bit.ly/PV066f (Publicado en: http://www.carnivoreconservation.org/ )

 

Livestock Depredation by Wolves: Michael Francis (2004)

Summary/Abstract:
The state of Colorado expects recovering and dispersing wolf (Canis lupus and C. l. baileyi) populations to reach the state in the near future. Likewise, the western Distinct Population Segment of recovering gray wolves may be delisted soon. In preparation for this eventuality, the Colorado Division of Wildlife (CDOW) has initiated the development of a state wolf management plan in an effort to deal with the many controversial issues surrounding this topic, which includes the possible depredation upon livestock and other domestic animals by wolves. This paper deals specifically with cowcalf and sheep depredation and examines the actual threat to Colorado’s livestock industry as well as the threat to individual ranchers should wolves establish packs in the state. I found that while wolves prefer wild game and are less likely to depredate livestock when game is available, wolves are opportunistic and will depredate livestock. Such depredations will not likely have any detectable negative effect on overall livestock production in the state but individual ranchers could experience significant losses through surplus killing or chronic depredations, with sheep producers more likely to experience such losses. If Colorado desires to monitor the effects of depredations by wolves, qualified staff must be employed and depredation trends monitored to evaluate the impacts. I also found that management of threats to livestock through the development of long-term strategies and identification of threat inducing factors are important for determining future allocations of resources in the application of combinations of wolf management tools to minimize risks to livestock producers. Such strategies will need to be employed along with active wolf management by USDA Wildlife Services or CDOW, particularly in areas where chronic depredations and conflicts do arise(assuming eventual de-listing of the gray wolf from Endangered Species Act protections)."

Conclusion:
"In many parts of the world wolf depredation is simply a part of doing business in the livestock industry. However, Colorado ranchers have not had to deal with this problem for many generations now and the possibility of loss due to wolves is an issue of significant concern. With the strong possibility of wolf populations re-colonizing into Colorado in the near future, the possibility of livestock depredations resulting from wolves is a real concern that could significantly affect individual livestock producers."

Livestock Depredation by Wolves: Michael Francis (2004) http://bit.ly/U7NdWB Rocky Mountain Wolf Recovery Annual Reports. Paper 16. University of Nebraska - Lincoln (7-26-2004) http://digitalcommons.unl.edu/

Análisis de la problemática del lobo (canis lupus) en Euskadi: J. Echegaray, A. Illana Martínez et al, (2006)

"El lobo es el depredador más problemático y a la vez emblemático de Euskadi. Ha dejado una huella sin parangón en el mundo animal en lo que respecta al patrimonio vasco tanto en la cultura como en la mitología (Altuna 1971, Barandiarán 1972, Murga 1978), y figura hasta en el escudo de Bizkaia.

En la Comunidad Autónoma Vasca están presentes 13 especies de carnívoros terrestres y el 47% de las mismas se encuentran incluidos en alguna de las categorías de amenaza recogidas en los ámbitos internacional, nacional y/o regional (Álvarez et al. 1995, Álvarez et al. 1998). El lobo, en cuanto a su estatus legal, no figura ni siquiera como especie presente en el Catálogo Vasco de Especies Amenazadas (Álvarez et al. 1998), tampoco es especie cinegética, pero es objeto de fuertes controles poblacionales por su conflictividad con la ganadería extensiva, especialmente el ovino de raza “latxa”. Su presencia en el Euskadi está sometida a fuertes variaciones temporales tanto en lo que se refiere a número de efectivos como a su área de distribución” (Sáenz de Buruaga et al. 1994, Echegaray et al. 2003).

En lo que atañe a la disponibilidad de presas naturales, existe una corriente de opinión generalizada de que los lobos en Euskadi sólo depredan ganado o son carroñeros y asiduos visitantes de basuras por carecer de ungulados silvestres. El corzo parece ser un factor relevante en la presencia del lobo y el posible asentamiento de nuevos grupos de lobos tendría como uno de los factores más importantes la presencia y densidad de corzos en dichas zonas. La zona ocupada por los lobos en Bizkaia es la de mayor densidad de corzos (comarca de Encartaciones) y presenta una discreta población de ciervos procedentes de repoblaciones cinegéticas en los años 80 en Karrantza. En áreas como el parque natural asturiano de Somiedo o el norte de Italia se observa una selección preferente por los corzos y los jabalíes (Llaneza 1996, Nores 2005, Mattlioti 1995)."

Sumario:
 

Análisis de daños al ganado
Datos oficiales
Ataques de perros
Introducción de Mastines
Mortandad no natural
Ecosistemas Holárticos
Soluciones posibles

Análisis de la problemática del lobo (canis lupus) en Euskadi: J. Echegaray, A. Illana Martínez et al, (2006) http://bit.ly/Pz57BR Sustrai: revista agropesquera, Nº. 77, 2006, págs. 48-51. (Publicada por el Gobierno Vasco: http://www.nasdap.ejgv.euskadi.net/ )

A project of economic-ecological analysis of wolf-livestock interactions in Spain: D.K. Kirby, L. Boitani & R. Ruiz (2004)

Summary:

"Extensive livestock systems are with increasing frequency facing complex issues balancing the social and economic needs of the farmers and the maintenance of traditional farming systems, with environmental and wildlife conservation considerations. This type of human-wildlife conflict is illustrated by the introduction of wolf conservation measures in Europe in areas where sheep are extensively managed. This has occurred in the Basque region of Spain, where sheep farmers are being severely affected by wolf predation. Although compensation payments are available to farmers, their real impact in reducing the social and economic costs of wolf presence have yet to be analysed, and it may be that the continuation of extensive sheep farming and improvement of livestock quality are being compromised at the current level of financial schemes. It is therefore desirable that the actual level of economic damage to extensive sheep farmers is assessed and quantified so that the trade-offs between wolf conservation and the preservation of the extensive livestock systems can be objectively accomplished. This project aims to provide policy guidelines for the management of livestock and wolf populations in the Basque country at both farm and landscape levels. The proposed methodology will take an interdisciplinary approach, including farmerparticipatory techniques and economic-ecological analysis and modelling. The project will integrate economic optimisation of livestock production with GIS-based predictive modelling of wolf movements and of wolf-livestock interactions. Integrating ecological and economic modelling within a GIS framework will allow area-specific predictions to be made of changes in wolf populations and/or sheep management practices on the economic impact of wolf predation on sheep farming. The output from this work will be used to make policy recommendations for the future management of the wolf-livestock interactions."

Conclusions:

"[...] Although compensation payments for livestock damage have been provided within Europe for over two decades, assessment of the effectiveness of these programmes in terms of farm livelihoods and wolf conservation has never been made. This research will therefore provide the first opportunity to develop and disseminate methodologies for assessing the efficacy of compensation payments in the dual context of wolf conservation and farming sustainability. In addition, the results produced will give rise to the development of appropriate policy guidelines in this field.

The project’s ultimate objective is to produce policy guidelines for reducing conflicts arising between wildlife and human interests in Spain. It is anticipated that this methodology could be applied to other wildlife-human interactions, both within and outwith Europe. Although set within a unique set of ecological, cultural and economic circumstances, these issues will have similar underlying principles to which the same approach may be taken."

A project of economic-ecological analysis of wolf-livestock interactions in Spain: D.K. Kirby, L. Boitani & R. Ruiz (2004) http://bit.ly/NZJ2PN Publicado por Centre international de hautes études agronomiques méditerranéennes: http://www.ciheam.org/
 

Primavera de lobos: Juan Carlos Blanco (2007)

"Resumen

En este artículo se analizan distintos aspectos biológicos, etológicos y de hábitat del lobo, así como su situación no solamente en España, país que tiene el privilegio de albergar la población de lobos más numerosa de Europa occidental, sino también en el resto del mundo.

Escoba florida, loba parida

La loba tiene buenos motivos para ser reservada. Está preñada y busca un lugar secreto para parir.

El lobo en el campo

El tamaño de los lobos muestra un gradiente latitudinal acorde con la regla ecológica de Bergmann, de tal forma que los más grandes viven en los países más septentrionales. Los lobos ibéricos tienen un tamaño medio.

Lobos y perros

Los lobos y los perros se hibridan sin problemas en cautividad produciendo descendencia fértil, y también lo hacen en libertad cuando las poblaciones están muy fragmentadas o han quedado muy reducidas a causa de la persecución.

Cazadores del Norte

Originalmente, el lobo era uno de los mamíferos con área de distribución natural más amplia en el mundo, pues ocupaba la mayor parte del Hemisferio Norte por encima del paralelo 20. [...] Después de siglos de regresión generalizada, en las últimas décadas están aumentando al menos en Norteamérica y la mayor parte de Europa gracias a la nueva conciencia conservacionista.

Estudiando a una especie esquiva

Tras siglos de persecución, los lobos han aprendido a moverse con el sigilo de las sombras, duermen durante el día y buscan su alimento por la noche, cuando la oscuridad los oculta de las miradas del hombre. Esta vida clandestina convierte su estudio en una difícil tarea, y con los métodos tradicionales sólo podemos recoger datos anecdóticos.

[...] Por este motivo se han desarrollado técnicas específicas de investigación que nos permiten obtener datos que se aplican también a otros carnívoros. Uno de los principales métodos de estudio es el radiomarcaje. [...] Además del radiomarcaje, el análisis de excrementos permite conocer su alimentación.

Desde la alta montaña hasta la llanura cerealista.

Es cierto que los lobos pueden vivir en muchos medios diferentes, pero no todos son igualmente favorables para la especie. Su hábitat óptimo en España presenta tres características esenciales: aporta protección contra el hombre, tiene suficiente alimento y no propicia conflictos entre los lobos y los intereses humanos. [...] La actitud por parte del hombre es un elemento del hábitat al menos tan importante como la cobertura vegetal o el alimento natural.

El menú del lobo: corzos, jabalíes...

En España su dieta es muy diversa y varía en las diferentes regiones, pero la dependencia del ganado doméstico (que, en su mayor parte, es consumido como carroña) y de los ungulados silvestres es un rasgo común en casi todo el país. [...] Los lobos cazan las grandes presas de forma cooperativa, y a veces también las pequeñas. [...] Normalmente, eligen a los ejemplares más vulnerables, es decir, las crías, los ejemplares viejos y los enfermos.

... Y ganado

La depredación del lobo sobre el ganado doméstico constituye un fenómeno universal, y es la principal causa de la tradicional persecución por parte del hombre. [...] La depredación sobre el ganado es desproporcionadamente elevada en las áreas de montaña (el 77% de los daños se producen en estas zonas, que sólo albergan el 20% de los lobos del país) a causa de la falta de vigilancia del ganado lobadas, en las que los cánidos matan muchos más individuos de los que pueden en régimen extensivo. Un factor común a la depredación sobre el ganado son las comer. [...] Esta depredación y denota la falta de inhibición de la agresividad cuando atacan animales con escasos excesiva se produce esporádicamente en todas las especies de carnívoros conocidos, mecanismos de defensa.

El territorio del lobo

Como veremos más adelante, los lobos viven en manadas, cuyos miembros comparten un territorio común. Las poblaciones se organizan en un mosaico de territorios contiguos o con un grado variable de solapamiento. Por encima de este mosaico se sitúa una nube de ejemplares solitarios llamados transeúntes o flotantes, que tienen movimientos irregulares e impredecibles. Los límites de los territorios se anuncian a las manadas vecinas con señales acústicas —los famosos aullidos— y mediante el marcaje olfativo con excrementos y orina. Los encuentros entre manadas son raros pero pueden dar lugar a combates que con cierta frecuencia acaban en la muerte de algún ejemplar. [...] En los lugares salvajes con escasa presencia humana, pueden estar activos tanto de día como de noche, pero en España y en otros países densamente humanizados, concentran su actividad en la noche y suelen permanecer dormidos casi todo el día en alguna zona de densa vegetación para evitar al hombre. [...] En su ciclo anual podemos considerar dos períodos distintos: el primero se sitúa en la temporada de cría, entre mayo y octubre, y el segundo comprende el resto del año. En la temporada de cría, los lobos de la manada se centran alrededor de la madriguera y las áreas aledañas.

El comportamiento social en el seno de la manada

Como es sabido, los lobos viven en manadas jerarquizadas, compuestas en general por miembros de la misma familia. [...] En esencia, ésta es la estructura típica de una manada. Los miembros de la única pareja reproductora son casi siempre los individuos dominantes, y los jóvenes del año anterior  colaboran en la cría, alimentando, cuidando y jugando con los nuevos lobeznos. [...] En las zonas donde la población está saturada, los flotantes pueden constituir hasta el 30% de los ejemplares de la población. [...] Tanto en Norteamérica como en España las manadas estables de 5 a 10 individuos son las más habituales.

Una nueva camada cada primavera

En España el celo tiene lugar en marzo y tras 63 días de gestación se producen los partos (entre abril y junio), por lo general más tardíos en las regiones más septentrionales. En los grupos estables normalmente no copulan más que los individuos dominantes de cada sexo, por lo que sólo se produce una camada por manada.

Conservar una especie conflictiva

El mayor pecado del lobo consiste en atacar al ganado que no está suficientemente protegido. Por este motivo ha sido tradicionalmente perseguido por todas las culturas pastoriles euroasiáticas. [...] La especie ocupaba la mayor parte de España hasta mediados del siglo XIX, pero la creciente presión humana la llevó a una situación crítica hacia 1970. Desde entonces, las poblaciones se han recuperado de forma notable como consecuencia de la nueva conciencia conservacionista. [...] Sin embargo, el lobo ha desaparecido en los últimos 40 años de varias regiones del sur de España, y en Sierra Morena se encuentra en la actualidad en serio peligro de extinción por la persecución ilegal en las grandes para los ungulados silvestres. fincas privadas de caza mayor, donde se los percibe como animales perjudiciales. [...] el lobo encarna símbolos opuestos para los habitantes urbanos y los rurales. Los primeros están decididamente a favor del cánido, en el que ven un representante de la naturaleza salvaje y un elemento indispensable del equilibrio natural al que no tenemos derecho a matar aunque cause daños al ganado. Los segundos son hostiles a los lobos, aprecian sobre todo su valor como pieza de caza y consideran que su aceptación mejoraría si los lobos reportaran algún beneficio económico. En los países occidentales, en la parte más extrema del sector urbano, en los últimos años proliferan grupos ecologistas radicales que mitifican al lobo, rechazan los resultados de los estudios científicos y se oponen a cualquier tipo de manejo o control de las poblaciones. Su agresividad promueve el radicalismo de los sectores antilobo, hasta el punto de convertir las polémicas sobre la gestión de la especie en auténticas guerras sociales."

Juan Carlos Blanco: Primavera de lobos (Ars Medica. Revista de Humanidades 2007; 1:3-19) http://bit.ly/SM8NOR