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

Large predators limit herbivore densities in northern forest ecosystems: William J. Ripple & Robert L. Beschta (2012)

Abstract:

Wolves primarily prey on ungulates that are considerably larger and

possess formidable defenses in their antlers, hooves, and behavioral

responses to predator attacks. Thus, many wolf predation attempts are

unsuccessful. Photo: Cindy Goeddel (http://goeddelphotography.com/ )

"There is a lack of scientific consensus about how top-down and bottom-up forces interact to structure terrestrial ecosystems. This is especially true for systems with large carnivore and herbivore species where the effects of predation versus food limitation on herbivores are controversial. Uncertainty exists whether top-down forces driven by large carnivores are common, and if so, how their influences vary with predator guild composition and primary productivity. Based on data and information in 42 published studies from over a 50-year time span, we analyzed the composition of large predator guilds and prey densities across a productivity gradient in boreal and temperate forests of North America and Eurasia. We found that predation by large mammalian carnivores, especially sympatric gray wolves (Canis lupus) and bears (Ursus spp.), apparently limits densities of large mammalian herbivores. We found that cervid densities, measured in deer equivalents, averaged nearly six times greater in areas without wolves compared to areas with wolves. In areas with wolves, herbivore density increased only slightly with increasing productivity. These predator effects are consistent with the exploitation ecosystems hypothesis and appear to occur across a broad range of net primary productivities. Results are also consistent with theory on trophic cascades, suggesting widespread and topdown forcing by large carnivores on large herbivores in forest biomes across the northern hemisphere. These findings have important conservation implications involving not only the management of large carnivores but also that of large herbivores and plant communities."

Introduction:

Conceptual diagram of trophic cascades showing hypothesized
predator densities, herbivore densities, and plant damage for populations
across a productivity gradient in the presence (left column) and absence
(right column) of large predators in productive ecosystems with NPP>
0.7 kg/m2/year (based on Oksanen 1992; Oksanen et al. 1981)

"[...] Consistent with the GWH (Hairston et al. 1960) and the EEH (Oksanen 1992), we hypothesize a set of trophic interactions across a gradient of primary productivity for boreal and temperate ecosystems that are productive enough to support carnivores. In systems with intact and ecologically effective large carnivore guilds (i.e., tri-trophic cascades, left side of Fig. 1), we expect (1) carnivore densities to be resource-limited and positively correlated with primary productivity and (2) herbivores mainly predator-limited, such that herbivore density increases only slightly with increasing productivity. In this system, herbivore damage to palatable plants would be relatively low regardless of productivity. Although not rigorously tested herein, EEH predicts that when the removal of large predators occurs (i.e., truncated trophic cascades, right side of Fig. 1), herbivore density would be positively correlated with productivity and damage to palatable plants relatively high regardless of primary productivity.

 

Understanding the effects of large predator and herbivore populations upon native plant communities has potentially important conservation implications. If large predators reduce plant damage by altering cervid behavior and limiting their densities, the maintenance of large predators across landscapes could be a crucial option for sustaining the ecological integrity of ecosystems (Estes et al. 2011; Miller et al. 2001; Soulé et al. 2003; Terborgh and Estes 2010). Furthermore, in areas where large predators have been displaced or locally extirpated, their reintroduction may represent a particularly effective approach for passively restoring those ecosystems."

Conclusions:

Wolf densities (y) as a function of net primary productivity (x),
where y013.08x-3.49; SEE010.0, R200.35, p00.008, and n019. SEE
Standard error of the estimate

"On average, we found cervid densities in systems without wolves to be approximately six times greater than that of systems with wolves (2.6 vs. 15.5 DE/km2). Cervid densities in systems with wolves and bears ranged from 0.03 to 8.4 DE/km2 with density increasing slightly with NPP.
These results could serve as benchmarks, based on the productivity of a particular region, for designing and evaluating the management of non-migratory cervid populations, where the goal is to emulate the range of densities typically found when wolves and bears are present in northern forests. Additionally, the wolf densities presented herein (x ¼ 17:8=1000km2, range 2.3–40.2) could also be used as benchmarks for assessing wolf management goals across a range of productivities. In general, regions with higher productivity and intact habitat have the capability to support higher wolf densities than areas with lower productivity (Fig. 4)."

 

"Recent research suggests that conservation programs based on the presence of apex predators may lead to broader biodiversity benefits (Sergio et al. 2008). Thus, sites containing intact carnivore guilds and which retain ecological processes should be considered as priority areas for both research and conservation planning (Woodroffe and Ginsberg 2005). Additionally, repatriating large carnivores to portions of their former range may still be possible and could have positive ecological effects. For example, the reintroduction or recolonization of wolves, decades after extirpation, has shown to positively affect tree and shrub recruitment at some sites on ungulate winter ranges where cervids seasonally migrate (Beschta and Ripple 2007; Ripple and Beschta 2012). More research is needed to determine to what extent large predators structure ecosystems in areas with both migrating and nonmigrating large herbivores. The preservation or recovery of large predators may thus represent an important conservation need for helping to maintain the resiliency of northern forest ecosystems, especially in the face of a rapidly changing climate."

 
Large predators limit herbivore densities in northern forest ecosystems: William J. Ripple & Robert L. Beschta (2012) http://bit.ly/PAshaN Eur J Wildl Res (DOI 10.1007/s10344-012-0623-5) 20 February 2012 Springer-Verlag 2012 (Publicado en http://www.cof.orst.edu/ )

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/

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