Open Access
How to translate text using browser tools
6 May 2020 Pack size in humanized landscapes: the Iberian wolf population
Alberto Fernández-Gil, Mario Quevedo, Luis M. Barrientos, Angel Nuño, Javier Naves, Miguel de Gabriel, Andrés Ordiz, Eloy Revilla
Author Affiliations +

Group living is an important behavioral feature in some species of mammals, although somewhat uncommon in the Order Carnivora. Wolves Canis lupus are highly social and cooperative carnivores that live in family groups, i.e. packs. The number of wolves in a pack affects social, reproductive and predatory behavior, thus conditioning population dynamics. Despite its relevance to management decisions, pack size has not been thoroughly studied in populations inhabiting human dominated landscapes such as the Iberian Peninsula. We estimated variation of wolf pack size from 1990 to 2018 in northern Spain, both in winter and summer. Winter data corresponded to direct observations and snow tracking at 42 localities (n = 253 data, 160 pack-years), whereas summer data corresponded to observations at rendezvous sites at 22 localities (n = 237 data, 43 pack-years). We estimated average pack size from the largest number of wolves recorded at each locality and year. Winter pack size averaged 4.2 ± 1.7 (mean ± SD) individuals. At summer rendezvous sites adult/subadult wolves (older than one year) averaged 3.1 ± 1.3 individuals, whereas pups averaged 4.0 ± 1.9. Generalized linear mixed models (GLMM) showed that pack size declined through the winter from 4.9 (4.2–5.6, 95% CI) wolves in November to 3.8 (2.9–4.9, 95% CI) wolves in April. We found no trend in pack size, neither in winter nor in summer. We discuss our results compared with other studies and populations worldwide, and its usefulness to comprehend the dynamics of this vulnerable population.

Group living is a behavioral characteristic in some mammalian species, but in the Order Carnivora only 10–15% species live in groups, a strategy that entails specific selective pressures (Creel and Macdonald 1995). In social and cooperative species of carnivores, most individuals live in social units (i.e. groups, packs, clans, prides) with complex dynamics that affect parameters such as litter size, pup and adult survival, dispersal and, ultimately, population dynamics; group size can also influence prey choice, kill rates and interactions among conspecifics and with other species. In addition, reproductive output can be determined by group living through reproductive suppression of subordinate individuals (Macdonald and Kays 2005).

Wolf populations are organized in cooperative social units named packs (Mech and Boitani 2003). Packs of wolves are highly territorial and maintain exclusive areas by means of visual, olfactory and acoustic communication. Their basic composition is a breeding pair, the dominant male and female that usually monopolize reproduction, plus their offspring and other adults or sub-adult wolves (Mech 1999). Wolf pack size ranges from two to more than twelve individuals, and varies seasonally from lower in late winter to higher in summer after parturitions (Mech and Boitani 2003). It may also vary widely among populations (Fuller et al. 2003), and variation in pack size is one of the determinants of wolf population size (Hayes and Harestad 2000, Fuller et al. 2003, Apollonio et al. 2004), together with prey biomass and territory density (Kittle et al 2015, Mech and Barber-Meyer 2015). Pack size variation and composition affects pup survival and reproductive success (Harrington et al. 1983, Peterson et al. 1984), as well as kill rates, food intake, predation rates and interactions with neighboring groups (Vucetich et al. 2002, Metz et al. 2011).

The cohesiveness of individuals within a pack has been related to the capability of killing large prey, and the outcome of competition with scavengers (Schmidt and Mech 1997, Vucetich et al. 2004). Cohesion among wolves in a pack is affected by the number of individuals, the composition of the group (i.e. age and sex of the members), the season, and also by abiotic factors like snow depth (Fuller 1991, Mech and Boitani 2003). Pack cohesion can influence the estimates of pack size, and thus ultimately of population size (Chapron et al. 2016). Estimates of pack size have been commonly derived from direct observations, or counting the track-sets of packs in snow (e.g. compilation by Fuller et al. 2003), and more recently from non-invasive genetic sampling at rendezvous sites and along tracks (Stenglein et al. 2011, Liberg et al. 2012). Nevertheless, potential factors affecting the counts of individuals in packs as well as variation and uncertainty have not often been described in detail (Fuller et al. 2003, Barber-Meyer and Mech 2015).

A currently isolated wolf population inhabits humanized landscapes of the Iberian Peninsula, in Spain and Portugal (Chapron et al. 2014). The population, which includes about 350 wolf packs (MAGRAMA 2016, Torres and Fonseca 2016), is strictly protected in Portugal (listed as Endangered, Cabral et al. 2005), and is under culling and hunting management in most of its Spanish range (Quevedo et al. 2019). Several authors have discussed pack size in this population (Barrientos 2000, Llaneza et al. 2009, Fernández-Gil et al. 2010, Blanco and Cortés 2012, Fernández-Gil 2013) but evaluation of determinants and variability of pack size are generally lacking. Our goals were estimating average pack size and evaluating its seasonal and long-term variation by using direct observations and track sets, while exploring factors that could affect those estimates.

Figure 1.

Localities included in the study. Winter data (blue dots) were collected in the Cantabrian Range (n = 42 localities), while summer data (red dots) were collected in the Duero Plateau and Montes de León mountain range (n = 22 localities). Grey shading shows a 10 × 10 km grid covering the approximate distribution of the Iberian wolf population in Spain and Portugal (sensu Chapron et al. 2014).


Material and methods

Study areas

We collected data at 42 and 22 localities in the winter and summer areas, respectively. Winter data were gathered in the Cantabrian Mountains and nearby highlands, while summer data were collected in the Duero Plateau and Montes de León mountain range near the border with Portugal (Fig. 1). Several summer localities were less than 50 km away from winter locations, while western and easternmost winter localities were more than 200 km apart (Fig. 1).

The Cantabrian Range and Montes de León hold semi-natural areas of deciduous forests interspersed with shrublands up to the subalpine level (1800 m a.s.l.), and pastures where extensive livestock grazing is an important activity. The Duero Plateau is an agricultural steppe averaging 800 m a.s.l. with remnants of sub-Mediterranean forests of oak and pine. It harbors extensively managed sheep flocks, and livestock farms. In the Cantabrian Range and Montes de León wolves feed upon wild (red and roe deer, wild boar, chamois, ibex) and, to a lesser extent, domestic ungulates, whereas in the Duero Plateau carrion farm offal is an important diet source alongside ungulates (roe deer, wild boar) and Lagomorpha (Cuesta et al 1991).

Winter data

We collected wolf observations from 2000 to 2018 in winter, between November and April, i.e. between the abandonment of rendezvous-sites (the places where pups are fed until they can travel with the rest of the pack) and the births of the following breeding season.

We collected data on winter travelling packs (sensu Messier 1985, Ballard et al. 1995), i.e. the number of wolves travelling together (Schmidt et al. 2008), a metric commonly used in demographic studies of wolves (Fuller et al. 2003). We searched for track sets in the snow and used spotting scopes at dawn to look for wolves from vantage points. We focused on areas regularly used by wolves, mostly ridges, mountain passes and unpaved roads. We retained for analyses observations that met the following criteria: 1) direct observation of two or more travelling wolves lasting at least 10 min; 2) track sets on snow of at least 1 km including at least two wolves (i.e. the minimum number of wolves in a pack; Fuller et al. 2003, Ausband et al. 2014). Criteria to determine the number of individuals through direct observations and snow tracks were thus roughly equivalent in terms of traveled distances (Frame et al. 2004). We discarded for example observations of lone wolves, unclear or short track sets or observations of resting packs. All winter data were collected by either one of two observers: any locality could be searched by any of both, but at different dates. Each record included the number of individuals, location, date, observer and method (direct observation versus snow tracking). We used vantage points consistently and searched for snow track sets at specific locations; thus for a given combination of pack and year we assumed that data obtained at a specific location and year belonged to the same pack.

Data on snow cover were gathered from the NASA National Snow and Ice Data Center (Hall and Riggs 2016a, b). Snow cover was measured at each pack location and closest available date (i.e. maximum of eight days of difference) as the proportion of terrain covered by snow in 500 m cells and, when data was missing at that resolution, in 0.05° cells (about 4.3 × 5.5 km). Data on snow depth was not available.

Table 1.

Description of variables considered in generalized linear mixed models (GLMMs).


Summer data

We collected direct observations at rendezvous sites between 1990 and 2002, from July to October. In the Iberian Peninsula, pups are usually born in late May, and remain at the den for up to five weeks (Vilá et al. 1995, Packard 2003); hence, pups are hardly seen before July. They can travel with the adults about mid-October, then abandoning rendezvous sites or using them solely as daily resting spots. We watched for wolves in areas where signs of intense use had been detected (e.g. heavily used trails with tracks and scats). Observations were conducted by a unique observer from vantage points at dawn or dusk, using spotting scopes, usually from 2 km or more to avoid disturbances. We considered two age classes because of their different behavior, attendance of rendezvous sites, and summer movement patterns (Packard 2003): pups (up to five months old), and adults/sub-adults (older than one year) can be easily differentiated by size overall aspect.

Variables and data analyses

We hypothesized that some methodological factors can affect the counts of individuals in a pack, e.g. counting method (two classes in winter) and observer; estimates can also be affected by abiotic factors (snow) that influence cohesion among individuals in a pack. We looked for long term trends by using year as a continuous variable along the studied periods in summer and winter. We also expected that the number of wolves in a group would decrease along both seasons because of mortality and dispersion, so we considered the month in which data were gathered as predictor, either as continuous (linear effects) or as a categorical (non-linear effects) variable (Table 1). We fitted generalized linear mixed models (GLMM; Poisson error distribution, log link function) to the number of wolves (n wolves) as response variable in winter, and observer, method, month, year and snow cover as predictors. We excluded from analysis those records lacking reliable data on snow cover. In summer, we fitted separate models to the number of adults and sub-adults, and pups (n ads and n pups, respectively), using month and year as predictors. We entered locality as random factor in all GLMMs. We used Akaike information criteria (AIC) and AIC weight (AICw) for model selection (Burnham and Anderson 2004, Burnham et al. 2011). Models were fitted using R package lme4 (Bates et al. 2015, <>). We computed an autocorrelation function ‘acf’ in R (2019) with the data of the maximum number of wolves per pack in winter.

Figure 2.

(A) Box plots of the number of wolves per observation in winter (n=253 data), (B) box plot of number of adult/sub-adult wolves and pups per observation in summer at rendezvous sites (n=186 and 150 for adults and pup, respectively).


We considered pack-year as the unit to estimate average pack size: the social unit at a given locality and the year in which data were obtained (Apollonio et al. 2004, Jedrzejewski et al. 2007). In winter, data between November and the following April were assigned to a unique winter season. We estimated average pack size from the largest count in each pack during any given year, following Śmietana and Wajda (1997) and Jedrzejewski et al. (2000). The full data set is available in Supplementary material Appendix 1 Table A1.



We obtained 253 winter records of travelling packs, at 42 localities, in 19 winters. Records per pack ranged 1–7 in any given winter, or pack-year (November 1999–April 2018, 160 pack-years). Individuals per pack ranged between 2 and 9 (Fig. 2A). Average number of wolves per pack was 4.2 ± 1.7 (± SD). The number of wolves per pack declined from 4.9 wolves (4.2–5.6, 95% CI) in November to 3.8 wolves (2.9–4.9, 95% CI) in April, based on the best model in Table 2. We found an effect of month on wolf counts per pack (Table 2), although the drop in average pack size was apparent in late winter (Fig. 2A). We found also a weak effect of ‘method', and no effect of ‘observer’, ‘year' or ‘snow cover’ on wolf counts (Table 2). Annual average pack size varied notably along the study period of 2000–2018 (Fig. 3), but we did not find a trend, or any significant autocorrelation in the maximum number of wolves per pack in winter (n = 160, Supplementary material Appendix 1 Fig. A1).


In summer, we obtained 237 observations of wolves at 22 localities, in 13 summers between 1990 and 2002 (43 pack-years). Observations per pack ranged 1–16 per year. We observed adults more frequently than pups (n = 186 and n = 150, respectively), and simultaneous observations of both adults and pups were rarer (n = 99). Adults and sub-adults ranged between 1 and 6 individuals per observation, whereas pups ranged between 1 and 8 (Fig. 2B). The largest pack observed in summer included 14 wolves: six adults and eight pups (full data set in Supplementary material Appendix 1 Table A1). The average number of adults/sub-adults per pack was 3.1 ± 1.3 (43 pack-years), while the average number of pups was 4.0 ± 1.9 (40 pack-years). The average total pack size in summer – estimated from simultaneous observations of both adults and pups – was 6.8 ± 2.5 (n = 99 observations; 31 pack-years). We did not find effects of ‘month' or ‘year’ on the number of adults/sub-adults or of pups (Table 2). We did not find a trend in summer pack size along the study period.


Our results of average pack size in winter (4.2 ± 1.7) were consistent with most European data, and even with reports along the south-eastern current range of the species in North America, e.g. Ontario and Wisconsin (Table 3). Summer estimates, on the other hand, showed much more variation, probably due at least partly to variability in methods. Winter methods seemed more consistent across studies and populations. Overall, we found wide variability in reporting certainty; several studies did not include the variance of their estimates (Table 3). Our dataset, based on a long series that used consistent methods, allowed reporting the variance of estimates, exploring changes in winter and summer wolf pack size, and evaluating some potential determinants of the counts. Note however that we obtained winter and summer data in relatively disjunct areas, where the staple diet of wolves is in principle different (Cuesta et al. 1991); therefore winter and summer estimates are not strictly comparable. North American data showed wider variation of winter pack size than European data (Table 3), probably reflecting wider variation in management of the studied populations (i.e. variation among years and zones in harvest and culling rates), and perhaps wider variation of prey base (Hayes and Gunson 1995, Fuller et al. 2003). Our winter estimates relied on so-called traveling packs, which have been implicitly regarded as roughly equivalent of actual pack size (Fuller et al. 2003). In winter, variation in pack cohesion may confound estimates of pack size based on traveling packs, especially in large ones (Peterson et al. 1984) that can split temporarily into foraging groups (Jedrzejewski et al. 2002). However, actual pack and traveling pack sizes do not differ significantly in winter, even in large packs (Dale et al. 1995). We expected high pack cohesion during winter in our study areas, as wolves must cope with unpredictable resources (mainly wild prey), both in space and time. Although it has been suggested that abiotic factors such as snow depth can affect cohesion (Fuller 1991), the most relevant factors affecting group cohesion are the same that drive group living in wolves, i.e. resource dispersion and competition with scavengers (Schmidt and Mech 1997, Vucetich et al. 2004, MacNulty et al. 2012, 2014). Usually high-ranking individuals do most kills, which means that few wolves commonly capitalize most predatory events (Sand et al. 2006), except when hunting very large prey (MacNulty et al. 2014). A considerable proportion of individuals in packs are pups from the previous breeding season, which do not usually hunt but have to remain close to the others to access food. Indeed, most wolf populations subsist primarily on prey they hunt, and thus cohesion should be high when the group travels along the territory during the period not occupied in feeding the pups at rendezvous sites. It is conceivable that only where important resources are predictable, at least spatially (e.g. farm offal, which at the same time does not require refined hunting skills), wolf groups may show looser cohesion, even during winter (Boitani 1992).We found that average pack size declined 22% in winter, a decline that may be explained by mortality and dispersal (Fuller et al. 2003). Human-related mortality can cause marked population declines over the winter, yet our study is one of the few that followed intra-seasonal changes in wolf pack size (Mech 1977, Jedrzejewska et al. 1996, which showed lower and higher declines, respectively, compared with our study; see also Table 3). A decline in winter pack size may also be due to temporal separation of the breeding pair from the pack at the onset of the mating season, in late winter. We did find a slightly higher frequency of packs of two wolves in February–April compared to November–January (21%, n = 79 pack-years, and 15%, n = 81 pack-years, respectively; Supplementary material Appendix 1 Table A1), but we do not expect that temporal separation of breeding pairs fully explained the observed late winter decline in pack size. In addition, the overall frequency of winter packs composed by just two wolves in our study (18%, 160 pack-years) was somewhat lower than in other studies (e.g. 25% in Adams et al 2008; 31% in Kittle et al. 2015; metrics estimated from the data reported in both studies).

Table 2.

Candidate models (GLMM, Poisson distribution, log link function, locality entered as random factor) fitted to number of wolves per pack in winter (n wolves n=240), and n ads (n=186) and n pups (n=150) in summer. AIC indicates Akaike information criterion; ΔAIC is the difference between best model (lowest AIC) and candidate models; AICw are AIC weights. We included parameter estimates β and standard errors (SE) for the best winter model.


Figure 3.

Box plot of winter pack size from 2000 to 2018. We used the highest count of each pack and year for the plot (n = 160 packs-year).


Table 3.

Compilation of worldwide estimates of wolf pack size; mean ± SD (* indicates SE). We calculated averages where possible in those studies that did not provided them directly (see column Notes). DO = direct observation; EH = elicited howling; SNT = snow-tracking; Misc = miscellaneous; Q = questionnaires; RT = radio-tracking; TS = tracks; NIG = non-invasive genetic sampling. Column n indicates pack-years.




There were fewer estimates of summer wolf pack size in the literature (Table 3), despite that summer observations can provide estimates of reproductive success. Our summer estimates included only metrics from packs that bred successfully, i.e. those that raised pups to late summer. Thus they do not indicate average number of pups per pack because wolf populations include substantial though variable proportion of non-breeding and unsuccessful packs: 15% in protected areas without lethal management (e.g. Denali National Park, Alaska, Mech et al. 1998), and up to 20% in protected areas with some lethal management (Adams et al. 2008). Mitchell et al. (2008) found that smaller packs living in areas with high human-caused mortality rates in the Rocky Mountains of the U.S. had lower probability of raising pups, and there were between 16 and 28% of unsuccessful packs.

Monitoring wolf pack size while clearly reporting methods, sample sizes, season and determinants of seasonal and inter-annual changes, remains an important aspect of population dynamics of this highly social species (Liberg et al. 2012, Chapron et al. 2016). Non-invasive genetic sampling has been recently used to ease estimates of wolf abundance at moderate spatial scales (Marucco et al. 2009, Stransbury et al. 2014), and multiple methods of population monitoring had been recently proposed (Ausband et al. 2014, Jiménez et al. 2016). However, estimating and monitoring the number of wolves that cooperate in a given territory are elusive tasks (Stenglein et al. 2011), which would always benefit from the natural history insights of direct observations and counts of snow track sets in the diverse contexts of wolf populations (Table 3). Particularly so in those situations when more logistically complex or expensive procedures (genetic sampling, radio-telemetry) cannot be used to guide estimates. The importance of using robust estimates of wolf pack size is emphasized by the fact that wolf management in many populations worldwide relies on hunting and culling (Boitani 2003). Moreover, wolf culling programs were implemented in many areas with poor understanding of population dynamics and ecological effects (Gehring et al. 2003, Wallach et al. 2009, Rutledge et al. 2010, Creel et al. 2015), an scenario likewise suggested for the wolf population in Spain (Quevedo et al. 2019).


Funding – ER was supported by grant CGL 2017-83045-R AEI/FEDER UE.



Adams, L. G. et al. 2008. Population dynamics and harvest characteristics of wolves in the Central Brooks Range, Alaska. – Wildl. Monogr. 170: 1–25. Google Scholar


Apollonio, M. et al. 2004. Wolves in the Casentinesi Forests: insights for wolf conservation in Italy from a protected area with rich wild prey community. – Biol. Conserv. 120: 249–260. Google Scholar


Ausband, D. E. et al. 2014. Monitoring gray wolf populations using multiple survey methods. – J. Wildl. Manage. 78: 335–346. Google Scholar


Ballard, W. B. et al. 1995. Use of line-intercept track sampling for estimating wolf densities. – In: Carbyn, L. N. et al. (eds), Ecology and conservation of wolves in a changing world. Canadian Circumpolar Institute, Edmonton, AB, Canada, pp. 469–480. Google Scholar


Barber-Meyer, S. M. and Mech, L. D. 2015. Gray wolf (Canis lupus) dyad monthly association rates by demographic group. – Can. Wildl. Biol. Manage. 4: 163–168. Google Scholar


Barrientos, L. M. 2000. Tamaño y composición de diferentes grupos de lobos en Castilla y León. – Galemys 12: 249–256. Google Scholar


Bates, D. et al. 2015. Fitting linear mixed-effects models using lme4. – J. Stat. Softw. 67: 1–48. Google Scholar


Bergerud, A. T. and Elliot, J. P. 1998. Wolf predation in a multiple-ungulate system in northern British Columbia. – Can. J. Zool. 76: 1551–1569. Google Scholar


Blanco, J. C. and Cortés, Y. 2012. Surveying wolves without snow: a critical review of the methods used in Spain. – Hystrix Ital. J. Mammal. 23: 35–48. Google Scholar


Boitani, L. 1992. Wolf research and conservation in Italy. – Biol. Conserv. 61: 125–132. Google Scholar


Boitani, L. 2003. Wolf conservation and recovery. – In: Mech, L. D. and Boitani, L. (eds), Wolves: behavior, ecology and conservation. Univ. of Chicago Press, pp. 317–340. Google Scholar


Burnham, K. P. and Anderson, D. R. 2004. Multimodel inference: understanding AIC and BIC in model selection. – Sociol. Methods Res. 33: 261–304. Google Scholar


Burnham, K. P. et al. 2011. AIC model selection and multimodel inference in behavioral ecology: some background, observations and comparisons. – Behav. Ecol. Sociobiol. 65: 23–35. Google Scholar


Cabral, M. J. et al. 2005. Livro Vermelho dos Vertebrados de Portugal: Peixes Dulciaquícolas e Migradores, Anfíbios, Répteis, Aves e Mamíferos. – Inst. da Conservação da Natureza, Lisboa, Portugal. Google Scholar


Caniglia, R. et al. 2014. Noninvasive sampling and genetic variability, pack structure and dynamics in an expanding wolf population. – J. Mammal. 95: 41–59. Google Scholar


Chapron, G. et al. 2014. Recovery of large carnivores in Europe's modern human-dominated landscapes. – Science 346: 1517–1519. Google Scholar


Chapron, G. et al. 2016. Estimating wolf (Canis lupus) population size from number of packs and an individual based model. – Ecol. Model. 339: 33–44. Google Scholar


Ciucci, P. and Boitani, L. 1999. Nine-year dynamics of a wolf pack in the northern Apennines (Italy). – Mammalia 63: 377–384. Google Scholar


Creel, S. and Macdonald, D. W. 1995. Sociality, group-size and reproductive suppression among carnivores. – Adv. Study Behav. 24: 203–257. Google Scholar


Creel, S. et al. 2015. Questionable policy for large carnivore hunting. – Science 350: 1473–1475. Google Scholar


Cuesta, L. et al. 1991. The trophic ecology of the Iberian wolf (Canis lupus signatus Cabrera, 1907). A new analysis of stomach's data. – Mammalia 55: 239–254. Google Scholar


Dale, B. W. et al. 1995. Winter wolf predation in a multiple ungulate prey system, Gates of the Arctic National Park, Alaska. – In: Carbyn, L. N. et al. (eds), Ecology and conservation of wolves in a changing world. Canadian Circumpolar Institute, Edmonton, AB, Canada, pp. 223–230. Google Scholar


Fernández-Gil, A. 2013. Comportamiento y conservación de grandes carnívoros en ambientes humanizados. Osos y lobos en la Cordillera Cantábrica. – PhD thesis, Univ. de Oviedo. < Scholar


Fernández-Gil, A. et al. 2010. Cómo estimar el tamaño medio de grupo en diferentes estaciones en las poblaciones Ibéricas de lobos. – In: Fernández-Gil, A. et al. (eds), Los lobos de la Península Ibérica. Propuestas para el diagnóstico de sus poblaciones. ASCEL, Palencia, pp. 69–90. Google Scholar


Fuller, T. K. 1991. Effect of snow depth on wolf activity and prey selection in north–central Minnesota. – Can. J. Zool. 69: 283–287. Google Scholar


Fuller, T. K. et al. 2003. Wolf population dynamics. – In: Mech, L. D. and Boitani, L. (eds), Wolves: behavior, ecology and conservation. Univ. of Chicago Press, pp. 161–191. Google Scholar


Frame, P. F. et al. 2004. Long foraging movement of a denning tundra wolf. – Arctic 57: 196–203. Google Scholar


Gehring, T. M. et al. 2003. Limits to plasticity in gray wolf, Canis lupus, pack structure: conservation implications for recovering populations. – Can. Field Nat. 117: 419–423. Google Scholar


Genov, P. et al. 2010. Dynamic of distribution and number of gray wolf (Canis lupus) during ten year period in Bulgaria. – 2nd Balkan Conf. on Biology, Univ. of Plovdiv. Biotechnol. and Biotechnol. EQ. 24/Special Edition. Google Scholar


Hall, D. K. and Riggs, G. A. 2016a. MODIS/Terra Snow Cover Daily L3 Global 500m Grid, Ver. 6. Boulder, Colorado USA. – NASA National Snow and Ice Data Center Distributed Active Archive Center., accessed: 03/01/2019Google Scholar


Hall, D. K. and Riggs, G. A. 2016b. MODIS/Terra Snow Cover Daily L3 Global 0.05Deg CMG, Ver. 6. Boulder, Colorado USA. – NASA National Snow and Ice Data Center Distributed Active Archive Center., accessed: 05/01/2019Google Scholar


Harrington, F. H. et al. 1983. Pack size and wolf pup survival: their relationship under varying ecological conditions. – Behav. Ecol. Sociobiol. 13: 19–26. Google Scholar


Hayes, R. D. and Gunson, J. R. 1995. Status and management of wolves in Canada. – In: Carbyn, L. N. et al. (eds), Ecology and conservation of wolves in a changing world. Canadian Circumpolar Institute, Edmonton, AB, Canada, pp. 21–33. Google Scholar


Hayes, R. D. and Harestad, A. S. 2000. Demography of a recovering wolf population in the Yukon. – Can. J. Zool. 78: 36–48. Google Scholar


Hayes, R. D. et al. 2003. Experimental reduction of wolves in the Yukon: ungulate responses and management implications. – Wildl. Monogr. 52: 35. Google Scholar


Hefner, R. and Geffen, E. 1999. Group size and home range of the Arabian wolf (Canis lupus) in southern Israel. – J. Mammal. 80: 611–619. Google Scholar


Heptner, V. G. and Naumov, N. P. 1998. Mammals of the Soviet Union, Volume II, Part 1a. – Science Publishers, Inc, New Hampshire. Google Scholar


Jedrzejewska, B. et al. 1996. Population dynamics of wolves Canis lupus in Bialowieza Primeval Forest (Poland and Belarus) in relation to hunting by humans, 1847–1993. – Mammal Rev. 26: 103–126. Google Scholar


Jedrzejewski, W. et al. 2000. Prey selection and predation by wolves in Bialowieza Primeval Forest, Poland. – J. Mammal. 81: 197–212. Google Scholar


Jedrzejewski, W. et al. 2002. Kill rates and predation by wolves on ungulate populations in Bialowieza Primeval Forest (Poland). – Ecology 83: 1341–1356. Google Scholar


Jedrzejewski, W. et al. 2007. Territory size of wolves Canis lupus: linking local (Bialowieza Primeval Forest, Poland) and holarctic-scale patterns. – Ecography 30: 66–76. Google Scholar


Jiménez, J. et al. 2016. Multimethod, multistate Bayesian hierarchical modeling approach for use in regional monitoring of wolves. – Conserv. Biol. 30: 883–893. Google Scholar


Kittle, A. M. et al. 2015. Wolves adapt territory size, not pack size to local habitat quality. – J. Anim. Ecol. 84: 1177–1186. Google Scholar


Kuzyk, G. W. et al. 2006. Pack size of wolves, Canis lupus, on caribou, Rangifer tarandus, winter ranges in westcentral Alberta. – Can. Field Nat. 120: 313–318. Google Scholar


Llaneza, L. et al. 2009. Seguimiento estival e invernal de lobos en los Ancares lucenses. – Galemys 21: 217–231. Google Scholar


Liberg, O. et al. 2012. Monitoring of wolves in Scandinavia. – Hystrix 23: 29–34. Google Scholar


Macdonald, D. W. and Kays, R. W. 2005. Carnivores of the world: an introduction. – In: Nowak, R. M. (ed), Walker's carnivores of the world. John Hopkins Univ. Press, pp. 1–67. Google Scholar


MacNulty, D. R. et al. 2012. Non-linear effects of group size on the success of wolves hunting elk. – Behav. Ecol. 23: 75–82. Google Scholar


MacNulty, D. R. et al. 2014. Influence of group size on the success of wolves hunting bison. – PLoS One 9: e112884. Google Scholar


MAGRAMA 2016. Censo 2012–2014 de lobo Ibérico (Canis lupus, Linnaeus, 1758) en España. – Ministerio de Agricultura, Alimentación y Medio Ambiente, Madrid. Google Scholar


Marucco, F. et al. 2009. Wolf survival and population trend using non-invasive capture–recapture techniques in the western Alps. – J. Appl. Ecol. 46: 1003–1010. Google Scholar


Mech, L. D. 1977. Productivity, mortality and population trends of wolves in northeastern Minnesota. – J. Mammal. 58: 559–574. Google Scholar


Mech, L. D. 1999. Alpha status, dominance and division of labor in wolf packs. – Can. J. Zool. 77: 1196–1203. Google Scholar


Mech, L. D. and Boitani, L. 2003. Wolf social ecology. – In: Mech, L. D. and Boitani, L. (eds), Wolves: behavior, ecology and conservation. Univ. of Chicago Press, pp. 1–34. Google Scholar


Mech, L. D. and Barber-Meyer, S. M. 2015. Yellowstone wolf (Canis lupus) density predicted by elk (Cervus elaphus) biomass. – Can. J. Zool. 93: 499–502. Google Scholar


Mech, L. D. et al. 1998. The wolves of Denali. – Univ. of Minnesota Press. Google Scholar


Messier, F. 1985. Social organization, spatial distribution and population density of wolves in relation to moose density. – Can. J. Zool. 63: 1068–1077. Google Scholar


Metz, M. C. et al. 2011. Effect of sociality and season on gray wolf (Canis lupus) foraging behavior: implications for estimating summer kill rate. – PLoS One 6: 1–10. Google Scholar


Mitchell, M. S. et al. 2008. Estimation of successful breeding pairs for wolves in the northern Rocky Mountains, USA. – J. Wildl. Manage. 72: 881–891. Google Scholar


Nowak, S. et al. 2008. Density and demography of wolf, Canis lupus population in the western-most part of the Polish Carpathian Mountains, 1996–2003. – Folia Zool. 57: 392–402. Google Scholar


Okarma, H. et al. 1998. Home ranges of wolves in Bialowieza Primeval Forest, Poland, compared with other Eurasian populations. – J. Mammal. 79: 842–852. Google Scholar


Packard, J. M. 2003. Wolf behavior: reproductive, social and intelligent. – In: Mech, L. D. and Boitani, L. (eds), Wolves: behavior, ecology and conservation. Univ. of Chicago Press, pp. 35–65. Google Scholar


Patterson, B. R. et al. 2004. Estimating wolf densities in forested areas using network sampling of tracks in snow. – Wildl. Soc. Bull. 32: 938–947. Google Scholar


Peterson, R. O. et al. 1984. Wolves of the Kenai Peninsula, Alaska. – Wildl. Monogr. 88: 1–52. Google Scholar


Quevedo, M. et al. 2019. Lethal management may hinder population recovery in Iberian wolves. – Biodivers. Conserv. 28: 415–432. Google Scholar


Rutledge, L. Y. et al. 2010. Protection from harvesting restores the natural social structure of eastern wolf packs. – Biol. Conserv. 143: 332–339. Google Scholar


Sand, H. et al. 2006. Effects of hunting group size, snow depth and age on the success of wolves hunting moose. – Anim. Behav. 72: 781–789. Google Scholar


Sand, H. et al. 2012. Assessing the influence of prey–predator ratio, prey age structure and packs size on wolf kill rates. – Oikos 121: 1454–1463. Google Scholar


Śmietana, W. and Wajda, J. 1997. Wolf numbers changes in Bieszczady National Park, Poland. – Acta Theriol. 42: 241–252. Google Scholar


Schmidt, P. A and Mech, L. D. 1997. Wolf pack size and food Acquisition. – Am. Nat. 150: 513–517. Google Scholar


Schmidt, K. et al. 2008. Reproductive behaviour of wild-living wolves in Białowieza Primeval Forest (Poland). – J. Ethol. 26: 69–78. Google Scholar


Stenglein, J. L. et al. 2011. Estimating gray wolf pack size and family relationships using noninvasive genetic sampling at rendezvous sites. – J. Mammal. 92: 784–795. Google Scholar


Stransbury, C. R. et al. 2014. A long-term population monitoring approach for a wide-ranging carnivore: noninvasive genetic sampling of gray wolf rendezvous sites in Idaho, USA. – J. Wildl. Manage. 78: 1040–1049. Google Scholar


Torres, R. T. and Fonseca, C. 2016. Perspectives on the Iberian wolf in Portugal: population trends and conservation threats. – Biodivers. Conserv. 25: 411–425. Google Scholar


Valdmann, H. et al. 2004. Group size changes and age/sex composition of harvested wolf (Canis lupus) in Estonia. – Baltic For. 10: 83–86. Google Scholar


Vilà, C. et al. 1995. Observations on the daily activity patterns in the Iberian wolf. – In: Carbyn, L. N. et al. (eds), Ecology and conservation of wolves in a changing world. Canadian Circumpolar Institute, Edmonton, AB, Canada, pp. 335–340. Google Scholar


Vucetich, J. A. et al. 2002. The effect of prey and predator densities on wolf predation. – Ecology 83: 3003–3011. Google Scholar


Vucetich, J. A. et al. 2004. Raven scavenging favours group foraging in wolves. – Anim. Behav. 67: 1117–1126. Google Scholar


Wabakken, P. et al. 2001. The recovery, distribution and population dynamics of wolves on the Scandinavian Peninsula, 1978–1998. – Can. J. Zool. 79: 710–725. Google Scholar


Wallach, A. D. et al. 2009. More than mere numbers: the impact of lethal control on the social stability of a top-order predator. – PLoS One 4: e6861. Google Scholar


Webb, N. F. et al. 2011. Demography of a harvested population of wolves (Canis lupus) in west-central Alberta, Canada. – Can. J. Zool. 89: 744–752. Google Scholar


Wydeven, A. P. et al. 2009. History, population growth and management of wolves in Wisconsin. – In: Wydeven, A. P. et al. (eds), Recovery of gray wolves in the Great Lakes Region of the United States. Springer, pp. 87–105. Google Scholar


Supplementary material (available online as Appendix wlb-00594 at <>). Appendix 1.

© 2020 The Authors. This is an Open Access article This work is licensed under the terms of a Creative Commons Attribution 4.0 International License (CC-BY). The license permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Alberto Fernández-Gil, Mario Quevedo, Luis M. Barrientos, Angel Nuño, Javier Naves, Miguel de Gabriel, Andrés Ordiz, and Eloy Revilla "Pack size in humanized landscapes: the Iberian wolf population," Wildlife Biology 2020(2), (6 May 2020).
Accepted: 30 January 2020; Published: 6 May 2020
Canis lupus
grey wolf
pack size
rendezvous sites
Back to Top