W

WIESEL, I. (2006)

Predatory and Foraging Behaviour of Brown Hyenas (Parahyaena brunnea (Thunberg, 1820)) at Cape Fur Seal (Arctocephalus pusillus pusillus Schreber, 1776) Colonies.

Diss. Uni Hamburg. 210 Seiten.

Volltext: https://ediss.sub.uni-hamburg.de/bitstream/ediss/1584/1/IWDissertation.pdf

Conclusions:

The predatory and foraging behaviour of brown hyenas (Parahyaena brunnea) was observed at mainland Cape fur seal (Arctocephalus pusillus pusillus) breeding colonies in the southern Namib Desert. The objectives of this study were to

(1) assess the availability, condition and accessibility of seals for brown hyenas,
(2) evaluate the importance of the coast for brown hyena abundance, movement and energy budget,
(3) determine factors influencing the foraging related time budget of brown hyenas,
(4) assess feeding preferences, and
(5) examine the consumption of prey.

Behavioural observations were conducted at the Van Reenen Bay seal colony and seal pup mortality data was recorded at the Wolf Bay seal colony.
GPS collars were fitted on coastal brown hyenas to determine their movement. Live seal pups were available for brown hyenas all year round, but their increasing size, mobility and activity, as well as the attendance pattern of adult females may influence the brown hyena’s foraging behaviour. Many dead pups were available to scavenge during the pupping season and represented an easy and safe way to obtain food.

In general, predators and prey are mutually influenced by each others behaviours. In Chapter 4 the anti-predator strategies of Cape fur seals towards brown hyenas were reviewed and assessed with regard to their influence on the hyena’s foraging strategies. Although Cape fur seals showed a near complete lack of anti-predator behaviour, the predator-prey system is possibly donor-controlled (Chapter 5) and the usual depensatory effect on prey populations that face novel or exotic predators is not expected (see Sinclair et al. 1998). The numerical response of predators to increased prey numbers as predicted by Holling (1959, 1965) could not be seen in this study (Chapter 5), and seasonality in the availability of seal pups, therefore, may limit brown hyena population growth, and may contribute to the maintenance of large home ranges despite localised food sources. However, coastal brown hyenas’ daily movements were less than that of inland ones, they have a lower field metabolic rate, and hence may consume less food.

Brown hyenas preferred to kill seal pups despite the availability of carrion (Chapter 6). The predation rate was unrelated to carrion availability, but the absolute number of kills was positively correlated to seal pup density. Increasing  seal pup density led to an increase in brown hyena capture rate and hunting efficiency. Furthermore the overabundance of easy and vulnerable prey led to surplus kills. However, brown hyenas foraged opportunistically by scavenging, killing and caching seal pups in proportion to their occurrence at the colony (Chapter 7 and 8), and hence, caused an additional impact on seal pup mortality by not only choosing the doomed surplus. The killing of seal pups seemed to be unrelated to hunger, and surplus killing occurred throughout the study period. Brown hyenas preferred to consume larger and heavier prey, but a large proportion of the brown hyena’s prey was only partially consumed (Chapter 8). Selectivity increased with seal pup density, and feeding and handling times per prey item were reduced. Brown hyenas showed a preference for brain tissue, and the consumption of brain tissue may quickly satisfy the brown hyena’s metabolic requirements, or may be important to keep a positive water balance. Although black-backed jackals (Canis mesomelas) outnumber brown hyenas and are their main competitors at seal colonies, they did not influence the brown hyena’s foraging strategy.

Brown hyenas, therefore, behave opportunistically regarding their feeding preferences and optimally regarding the consumption of seals. Seal pup density influences the brown hyena’s predatory and foraging behaviour, and seasonality in seal availability may limit brown hyena abundance and influence their movement patterns. Future observations of foraging brown hyenas outside the pupping season and at night could yield additional interesting information about adaptations in predatory and foraging behaviour to changes in seal behaviour, abundance and attendance.

wiesel-biblio

WIESEL, I. (2006)

Predatory and Foraging Behaviour of Brown Hyenas (Parahyaena brunnea (Thunberg, 1820)) at Cape Fur Seal (Arctocephalus pusillus pusillus Schreber, 1776) Colonies.

Diss. Uni Hamburg. 210 Seiten.

Volltext: https://ediss.sub.uni-hamburg.de/bitstream/ediss/1584/1/IWDissertation.pdf 

Conclusions

The predatory and foraging behaviour of brown hyenas (Parahyaena brunnea) was observed at mainland Cape fur seal (Arctocephalus pusillus pusillus)

breeding colonies in the southern Namib Desert. The objectives of this study were to

(1) assess the availability, condition and accessibility of seals for brown hyenas,

(2) evaluate the importance of the coast for brown hyena abundance, movement and energy budget,

(3) determine factors influencing the foraging related time budget of brown hyenas,

(4) assess feeding preferences, and

(5) examine the consumption of prey.

Behavioural observations were conducted at the Van Reenen Bay seal colony and seal pup mortality data was recorded at the Wolf Bay seal colony.

GPS collars were fitted on coastal brown hyenas to determine their movement. Live seal pups were available for brown hyenas all year round, but their

increasing size, mobility and activity, as well as the attendance pattern of adult females may influence the brown hyena’s foraging behaviour. Many dead pups

were available to scavenge during the pupping season and represented an easy and safe way to obtain food.

In general, predators and prey are mutually influenced by each others behaviours. In Chapter 4 the anti-predator strategies of Cape fur seals towards

brown hyenas were reviewed and assessed with regard to their influence on the hyena’s foraging strategies. Although Cape fur seals showed a near complete

lack of anti-predator behaviour, the predator-prey system is possibly donor-controlled (Chapter 5) and the usual depensatory effect on prey populations that

face novel or exotic predators is not expected (see Sinclair et al. 1998). The numerical response of predators to increased prey numbers as predicted by

Holling (1959, 1965) could not be seen in this study (Chapter 5), and seasonality in the availability of seal pups, therefore, may limit brown hyena population

growth, and may contribute to the maintenance of large home ranges despite localised food sources. However, coastal brown hyenas’ daily movements were

less than that of inland ones, they have a lower field metabolic rate, and hence may consume less food.

Brown hyenas preferred to kill seal pups despite the availability of carrion (Chapter 6). The predation rate was unrelated to carrion availability, but the

absolute number of kills was positively correlated to seal pup density. Increasing  seal pup density led to an increase in brown hyena capture rate and hunting

efficiency. Furthermore the overabundance of easy and vulnerable prey led to surplus kills.

However, brown hyenas foraged opportunistically by scavenging, killing and caching seal pups in proportion to their occurrence at the colony (Chapter 7

and 8), and hence, caused an additional impact on seal pup mortality by not only choosing the doomed surplus. The killing of seal pups seemed to be unrelated to hunger, and surplus killing occurred throughout the study period. Brown hyenas preferred to consume larger and heavier prey, but a large proportion of the brown hyena’s prey was only partially consumed (Chapter 8). Selectivity increased with seal pup density, and feeding and handling times per prey item were reduced.

Brown hyenas showed a preference for brain tissue, and the consumption of brain tissue may quickly satisfy the brown hyena’s metabolic requirements, or

may be important to keep a positive water balance. Although black-backed jackals (Canis mesomelas) outnumber brown hyenas and are their main competitors at seal colonies, they did not influence the brown hyena’s foraging strategy.

Brown hyenas, therefore, behave opportunistically regarding their feeding preferences and optimally regarding the consumption of seals. Seal pup density

influences the brown hyena’s predatory and foraging behaviour, and seasonality in seal availability may limit brown hyena abundance and influence their

movement patterns. Future observations of foraging brown hyenas outside the pupping season and at night could yield additional interesting information about adaptations in predatory and foraging behaviour to changes in seal behaviour, abundance and attendance.

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