Walia Special Edition on the Bale Mountains (2011) - Zoologische ...

Mean feeding rate (contributions/hour)
0.4
0.3
0.2
0.1
0
0 2 4 6 8 10
Number of helpers
dominant pair
non-breeders
Figure 3. Rate of feeding pups (contribution of solid foods per hour) by the dominant pair in
relation to the number of non-breeder helpers.
Pup survival
Between one and six pups emerged from each breeding den, and the observed average litter size for
20 litters born between 1988 and 1991 was 4.1 ± SE 0.36. While there was no significant difference
in litter size between years (F = 1.10, P = 0.379), the presence of an additional nursing female
(3,16)
at the den was associated with smaller litter size (see Allo-suckling below). The number of pups
emerging from the den was not significantly correlated with the number of adults and subadults at the
den (r = -0.26). The hypothesis that the number of non-breeding helpers enhances the reproductive
s
output of the group was not supported either. Pups survival at emergence was not correlated with
the number of non-breeding helpers (r = -0.26, n = 20, P > 0.05), nor was survival at whelping (r =
s s
-0.28, n = 20, P > 0.05). Similarly, there was no significant correlation with survival at six months,
one or two years and the number of non-breeding helpers.
Marino (2003b) looked at relationships between wolf group size and reproduction or survival
in a time series between 1988 and 2000 and confirmed the absence of a simple, direct relationship
between them. Instead, wolf density within territories appears to be negatively correlated to the
number of pups emerging from the den and pup survival and the survival of adults at the population
level correlates with density. Intriguingly, Tallents (2007) studied a subset of packs and found
litter size from emergence to 11 months was correlated with the number of adult males in the
pack, potentially through their role in securing high quality territories. There may be other effects
mediated by prey availability, with the impact of helpers possibly only being felt when times are
hard. Between weaning and ten months, juvenile survival was strongly correlated with the extent
of high quality foraging habitat, a pattern probably mediated through access to high prey densities
for the provisioning adults and subadults, and also through the juveniles’ own foraging success as
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