A note on responses of juvenile Javan lutungs (Trachypithecus auratus mauritius) against attempted predation by crested goshawks (Accipter trivirgatus)

On October 31st, 2013, we unexpectedly observed attempted predation of two juvenile Javan lutungs (Trachypithecus auratus mauritius) by adult crested goshawks (Accipter trivirgatus), in Pangandaran Nature Reserve, West Java, Indonesia. The goshawks flew over a group of feeding lutungs, attempting attacks only on juvenile lutungs from the rear, while emitting tweeting calls. The attacks involved two different birds (probably a pair) in turn from different directions. The attacks by the goshawks were repeated six times during our observation period (between 13:51 and 13:58), but none of the attempts was successful. During the attacks, no other lutungs in the group showed any anti-predator behavior (such as emitting alarm calls or escaping) against the goshawks perhaps because their body weight (6-10 kg) was much larger than that of goshawk (0.4-0.6 kg). To our knowledge, this is the first detailed report of hunting-related behavior to primates by this raptor species.