Variation in jackal numbers at the Van Reenen Bay seal colony with comment on likely importance of jackals as predators : short communications

Black-backed jackals Canis mesomelas at Van Reenen Bay Cape fur seal Arctocephalus pusillus pusillus colony in Namibia are largely dependent on seals as a food source. The jackal numbers showed both large daily and annual fluctuations during daylight hours. The highest number of jackals observed at one time was 86. The jackals tended to be present at the colony in larger numbers, and for longer periods, outside the seal pupping season than during it. During pupping seal placentas and dead pups are abundant. Outside the pupping season food may be more difficult for jackals to obtain and hence they are more diurnally active within the colony. An estimated 1 770 pups were killed or scavenged annually by jackals, i.e. 35.7% of the pups born at the colony. All jackal-kills observed were of seal pups. Jackal predation may be a factor in preventing mainland non-breeding seal colonies from developing into breeding colonies.