An example of endurance in an old Wolf, Canis lupus. L. David Mech (1997)

Lobo ártico portando una liebre ártica. 

Foto de L. David Mech. Fuente: Arctic. Noaa

An 11 to 13-year-old Arctic Wolf (Canis lupus arctos) was observed chasing a young Arctic Hare (Lepus arcticus) for 6 to 7 minutes and catching it. This provides an example of the degree of endurance of which an old wolf is capable.

Many descriptions of Wolves {Canis lupus) hunting have been published. However, none has provided a specific example of the endurance of which a known-old Wolf is capable. The observation of a female Wolf chasing, following, and tracking a White-tailed Deer (Odocoileus virginianus) for 21 km over a 130-minute period provides some insight, but that pursuit did not take place at high speed, and it involved a 2.5-year-old Wolf.

I describe here a chase by an 11 to 13-year-old, male Arctic Wolf (C /. arctos) of an Arctic Hare (Lepus arctos) that gives new insights into Wolf endurance. Wolves rarely live > 13 years in the wild and 16 in captivity (Mech 1988). I first observed the Wolf in this account on Ellesmere Island, Northwest Territories, Canada, during 1986 as a member of a pack that I habituated to my close presence (Mech 1988, 1995). The Wolf was distinguishable by a large wound on his left shoulder during 1986 and 1987 and by his behavior toward me from 1986 through 1996 as I observed him at distances of < 2 m.

In 1986, this Wolf must have been at least 1-year old because of his size, and his behavior seemed to be mature enough for a 2 or 3 -year- old animal, but he was not the dominant male of the pack. Because it is unlikely for a Wolf to remain in a pack more than three years, unless it assumes the breeding role (Gese and Mech 1991), this Wolf was probably not more than 3-years old in 1986.

In 1988, this Wolf which I called "Left Shoulder" became the breeding male in the pack, and he maintained that role through summer 1996; the only other males in the pack from 1988 to 1996 were his offspring (Mech 1995). In 1996, Left Shoulder's lower canine teeth were broken or worn to 1/3 to 1/2 their normal length. I made the following observation of this Wolf through binoculars from about 200 m away on 25 July 1996.

The terrain consisted primarily of lowhills covered by snow-free, bare soil and scree,  withlow hummocks in valleys. No vegetation was higher than a few cm. The Wolf and his mate had been hunting young hares intermittently from 0045 to 0250 when the  female headed back toward their den some 8 km away. The male slept from 0312 to 0535 and then arose. He walked NW approximately 100 m and suddenly veered E toward a crouching leveret about 10 m away and more-or-less upwind of him. He walked by the hare, passing 3-7 m by it and got about 7 m beyond, turned, and went back toward it. The hare then jumped up, and the chase began. The Wolf chased the hare for 6-7 minutes and almost caught it several times, but the hare's ability to make quick turns helped it elude the Wolf since the Wolf could not turn so sharply. The chase went back and forth, up and down gently sloping hills covering a distance with a maximum radius of an estimated 300 m. At times, the hare was as far as an estimated 30 m ahead of the Wolf. Finally at 0544 the hare seemed to tire and slow down, and the Wolf pounced on it.

The Wolf then rested, standing and panting from 0544 to 055 1 , when he lay down. He continued to lie and pant until 0606 when an associate of mine inadvertently disturbed him. The Wolf arose, carried the hare off, and cached it. He then slept from 0632 to 0712, and then left the area. I later dug up the cache and found that the leveret weighed 1 .45 kg.

This observation indicates that even an old Wolf can persist in a long pursuit at high speed for several minutes. That such a chase taxed the Wolf was evidenced by the animal's 22-minute rest before caching his quarry and his 40-minute sleep after that. In comparison, a yearling female Wolf observed chasing a young Arctic Hare on 10 July 1993 for 3 minutes rested 11 minutes before she began eating the hare. 

Mech, L. David. 1997. An example of endurance in an old Wolf, Canis lupus. Canadian Field-Naturalist 111(4): 654-655. http://bit.ly/OBH1s2 (Publicado en internet por http://www.biodiversitylibrary.org/ y  http://archive.org/  )
 

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/ )

Programa de actuaciones para la conservación del lobo (Canis lupus subsp. signatus Cabrera, 1907) en Andalucía. Informe semestral 2011 (Periodo julio 2010-enero 2011) (Junta de Andalucía, 2011)

Introducción: En el presente avance de información se describe la labor realizada de julio de 2010 a enero de 2011. Se han tomado medidas de gestión, peritaje de daños a ganado, realizado muestreos de detección de presencia de lobo y asesoramiento técnico a la Consejería de Medio Ambiente. La distribución conocida del lobo en el sur, se circunscribe a dos zonas de Sierra Morena, ocupando una superficie de unos 4.500 km2.tp://

Área de estudio. La retícula gris muestra la unidad de muestreo utilizada para los diferentes métodos, cada cuadrícula tiene unas dimensiones de 5x5 km. Los polígonos verdes delimitan los Parques Naturales, y los polígonos marrones el resto de Lugares de Interés Comunitario. Los polígonos rojos muestran la delimitación de la distribución del lobo estimada en el periodo 2005-2008.

Las técnicas de muestreo de lobo que más se usan se fundamentan en el reconocimiento y estudio de indicios de presencia. Las estimas de población del lobo, en la mayor parte del mundo donde el radio marcaje masivo no se aplica, se realizan combinando diferentes técnicas de muestreo. Las aplicadas en este programa han sido: los itinerarios de censo, las entrevistas, las esperas auditivas de aullidos, la observación en puntos fijos, ataques a ganado doméstico, observación y estudio de piezas de caza mayor matadas por los lobos. Ha intervenido un técnico durante todo el periodo y dos auxiliares en la realización de los muestreos de campo. En estos meses se han recorrido más de 45.000 km en desplazamientos con automóvil, a las zonas objeto de estudio. Los resultados a los que se llegan con estos métodos son tan sólo estimas poblacionales, no se pueden obtener valores numéricos absolutos para la población de lobo.

Cuadrículas muestreadas en el Núcleo Occidental en 2010. Cada estrella indica que al menos se ha realizado en la cuadrícula un muestreo con al menos una metodología.

Cuadrículas muestreadas en el Núcleo Oriental en 2010. Cada estrella indica que al menos se ha realizado en la cuadrícula un muestreo con al menos una metodología

Resultados

• Este semestre se ha caracterizado por la diversidad de las tareas realizadas (muestreos de campo, asesoramiento a ganaderos, peritaje de daños a ganado doméstico, instalación de pastor eléctrico, redacción de informes y otros documentos, formación auxiliares, etc.)
• Se han muestreado 122 cuadrículas diferentes de 5x5 km (3.050 km2) con al menos una de las metodologías de censo (itinerarios, simulación de aullidos y/o esperas). Encontrando la presencia del lobo en 38 cuadrículas diferentes (950 km2 ).
• La longitud total recorrida a pie ha sido de 677,88 km. Los rastros más hallados han sido los restos de presas seguidos de huellas. Los índices kilométricos de abundancia (IKA) dan un resultado de 0,031 rastros por kilómetro.
• Se han obtenido citas contrastadas procedentes de entrevistas, que nos aportan datos de presencia de lobo en 2010.
• De julio de 2010 a enero de 2011 solo se ha tramitado un ataque sobre ganado, y se ha acudido a otros tres que finalmente fueron desestimados.
• Se han encontrado 12 restos de ungulados salvajes capturados y/o consumidos por los lobos (ciervo (Cervus elaphus )= 8; gamo (Dama dama)=4).
• Las citas recopiladas apuntan que se mantiene la estima de población realizada en 2009 (siete grupos familiares en Sierra Morena, unos 49 lobos)
• Se ha instalado un pastor eléctrico en 2010 en Andújar. Dicho pastor eléctrico incluía la particularidad de traer piquetas móviles, pues el ganadero tiene varias fincas en el Parque Natural Sierra de Andújar y el ganado lo mueve.
• Se ha impartido un Seminario en la EBD sobre el lobo, actuaciones realizadas en la última década (Sevilla, 2010), se ha editado un folleto para el curso de formación de los agentes, aportación al documento: “Andalucía, naturaleza viva: La Gestión Activa del Medio Natural Andaluz”. Se actualiza la aportación al documento: “Diez años de Biodiversidad. Se redacta un breve informe sobre el ejemplar de lobo requisado en Huelva y depositado en el CREA de Córdoba.Se ha localizado al lobo en Sierra Morena de Andalucía.

Conclusiones

• Se han instalado manadas en zonas periféricas de ambos núcleos.
• La población total en Andalucía parece que se mantiene en los siete grupos (49 lobos) estimados en el periodo 2005-2008.
• Se ha tenido conocimiento de al menos un grupo familiar que se ha reproducido.
• Las medidas de gestión adoptadas en los últimos años con los ganaderos han sido muy exitosas para el lobo.

Recomendaciones de uso / Gestión

• Continuar indemnizando los daños al ganado, con el seguimiento de las poblaciones y con el fomento de medidas de prevención de ataques al ganado. Seguir asesorando a los ganaderos y propietarios de fincas en general. Cursos para Agentes de Medio Ambiente.
• Coordinar las medidas de seguimiento y conservación con la Administración de Castilla-La Mancha.

Programa de actuaciones para la conservación del lobo (Canis lupus subsp. signatus Cabrera, 1907) en Andalucía. Informe semestral 2011 (Periodo julio 2010-enero 2011) (Junta de Andalucía, 2011) http://bit.ly/TOKNQG (Publicado por http://www.juntadeandalucia.es/ )

The Costs of Carnivory: Chris Carbone, Amber Teacher, J. Marcus Rowcliffe. (2007)

Abstract:

"Mammalian carnivores fall into two broad dietary groups: smaller carnivores (<20 kg) that feed on very small prey (invertebrates and small vertebrates) and larger carnivores (>20 kg) that specialize in feeding on large vertebrates. We develop a model that predicts the mass-related energy budgets and limits of carnivore size within these groups. We show that the transition from small to large prey can be predicted by the maximization of net energy gain; larger carnivores achieve a higher net gain rate by concentrating on large prey. However, because it requires more energy to pursue and subdue large prey, this leads to a 2-fold step increase in energy expenditure, as well as increased intake. Across all species, energy expenditure and intake both follow a three-fourths scaling with body mass. However, when each dietary group is considered individually they both display a shallower scaling. This suggests that carnivores at the upper limits of each group are constrained by intake and adopt energy conserving strategies to counter this. Given predictions of expenditure and estimates of intake, we predict a maximum carnivore mass of approximately a ton, consistent with the largest extinct species. Our approach provides a framework for understanding carnivore energetics, size, and extinction dynamics."

The Costs of Carnivory: Chris Carbone, Amber Teacher, J. Marcus Rowcliffe. (2007) http://bit.ly/OPf9NT (Publicado en PLoS Biology http://www.plosbiology.org/ )

 

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Lo que sigue son extractos del artículo, sobre esta investigación, "El precio de ser carnívoro": http://bit.ly/QbzsVD tomados del blog La Singularidad Desnuda: http://singularidad.wordpress.com/

En este trabajo, los autores estudian la balanza energética de diferentes mamíferos carnívoros, y llegan a conclusiones sumamente interesantes, e incluso un tanto sorprendentes (aunque intuitivas a posteriori).

En primer lugar, han modelado el gasto energético diario (DEE – daily energy expenditure) como la suma del coste de caza, y el coste del descanso. Si M es la masa del depredador, este último es proporcional a M^0.75; en cuanto al coste de caza, se expresa como 10.7 M^0.684 v + 6.03 M^0.697, donde v es la velocidad que el animal es capaz de desarrollar (en ambos casos, estas expresiones provienen de modelos metabólicos). Usando el consumo energético diario (DEI – daily energy intake) como estimación del DEE (DEE=2/3·DEI), se puede observar cómo el modelo proporciona predicciones ajustadas y -lo más importante- muestra que hay un salto (lo podríamos llamar una transición de fase) al pasar de animales de menos de 14 kg a animales mayores. 

Este salto es muy interesante, pues indica que hay dos grupos claramente diferenciados en función de su balanza energética, los pequeños depredadores (por ejemplo, los linces), y los grandes depredadores (por ejemplo, los tigres). Más aún, si se trazan cotas inferiores y superiores (basadas en consideraciones metabólicas) al consumo energético diario, se observa que se predice un tamaño mínimo (en torno a los 100g) y un tamaño máximo (en torno a los 1,100 kg) para un mamífero depredador. 

 

Esto lo podemos ver también en términos de la ganancia energética neta (restando el gasto energético de la ganancia bruta obtenida por el consumo de presas). Ésta depende claramente del tipo de presa, por lo que hay una curva para los pequeños depredadores (que consumen invertebrados o pequeños vertebrados, mucho más pequeños que el propio depredador), y los grandes depredadores (que consumen presas iguales o mayores que el propio depredador). La curva que se obtiene es la siguiente:

Como puede verse, la ganancia neta desciende abruptamente para los pequeños depredadores por encima de los 10 kg. Aunque sique siendo positiva hasta los 85 kg, a partir de los 14 kg es más favorable comer presas grandes. El límite superior en torno a los 1,100 kg para los grandes depredadores mamíferos es además consistente con el registro fósil. El mayor mamífero carnívoro conocido, el Megistotherium osteothlastes, era un gigantesco animal de 3m de largo, y de una tonelada aproximada de peso. Por supuesto los dinosaurios carnívoros eran mayores, pero su tasa metabólica era inferior, lo que les permitió ser más grandes.