Cultural revolution in whale songs

Humpbacks have picked up a catchy tune sung by immigrants from a distant ocean. The song patterns of humpback whales (Megaptera novaeangliae) depend on where they live, with populations inhabiting different ocean basins normally singing quite distinct songs. Here we record a unique and radical song change in the song of humpback whales in the Pacific Ocean off the Australian east coast. Their song was replaced rapidly and completely by the song of the Australian west coast population from the Indian Ocean, apparently as a result of the introduction of only a small number of 'foreign' singers. Such a revolutionary change is unprecedented in animal cultural vocal traditions and suggests that novelty may stimulate change in humpback whale songs.

Whale sharks in Ningaloo Marine Park: managing tourism in an Australian marine protected area

The whale shark is the largest fish in the ocean, A tourism industry based on interacting with whale sharks has developed recently in Ningaloo Marine Park, off the coast of Western Australia, This is the only known, accessible place in the world where whale sharks congregate in significant numbers, Results from surveys of participants in the 'whale shark experience' are reported, with the experience found to be extremely satisfying for most consumers, Yet management questions relating to diver-to-shark separation distances, the appropriate number of operators, and the use of regulation, self-regulation and economic instruments, remain, The nexus between experiential aspects of the whale shark attraction and such management concerns is examined, and the usefulness of appropriate research in resolving management questions established, It is concluded that a judicious combination of management approaches is required to ensure the sustainable development of the whale shark tourism industry. (C) 1997 Elsevier Science Ltd.

Dysynchiria: Watching the mirror image of the unaffected limb elicits pain on the affected side

People with complex regional pain syndrome type 1 (CRPS1) watched a reflected image of their unaffected limb being touched and felt pain or paresthesia at the corresponding site on the affected limb. The authors suggest that allodynia and paresthesia can be mediated by the brain and that dysynchiria has implications for the understanding and management of CRPS1.

Influence of Observer Presence on Pacific Damsel Bug Behavior: Who is Watching Whom?

When direct observations are used to study animal behavior the presence of the observer may alter the animal and hence influence the data being collected, yet few studies have quantified this effect. We conducted direct observation studies in the glasshouse to assess the relative influence of observer presence on the behavior of Pacific damsel bugs, Nabis kinbergii, a potentially important predator of crop pests. Comparisons of predator activity, predator distribution, prey (Helicoverpa armigera) mortality and prey distribution between frequently observed and minimally observed treatments, during diurnal and nocturnal observation sessions showed that the frequency of observer presence had no apparent impact on Pacific damsel bug behavior. This is the first documented test of the impact of observer presence in an insect system. To place our results in context, we reviewed 15 papers on the influence of observer presence in a range of animals. We established that just over half of these papers found evidence for an effect. Nevertheless, direct observations should be useful in further studies of Pacific damsel bug behavior, and researchers using direct observations to study the behavior of other animals should be cognizant of observer effects during design and interpretation of their study.

Watching the brain oscillate: Identifying the neural correlates of illusory jitter

Moving borders defined by small luminance changes (or colour) can appear to jitter at a characteristic frequency when they are placed in close proximity to moving borders defined by large luminance changes (Arnold & Johnston, 2003). Using psychophysical techniques, we have now shown that illusory jitter can be generated when these different motion signals are shown selectively to either eye – implicating a cortical locus for illusory jitter generation. Using magneto-enceohalography (MEG) to record brain activity, we have also found that brain oscillations, of the same frequency as the illusory jitter rate, are enhanced when illusory jitter is experienced. This does not occur when observers are exposed to either isolated motion signals defined by small luminance changes (or colour) or to physical jitter of the same frequency as the illusory jitter. We believe therefore that the enhanced brain activity is related to illusory jitter generation rather than to jitter perception, or to isoluminant motion, per se. These observations support our hypothesis that this illusory jitter is generated in cortex by a dynamic feedback circuit. We believe that this circuit periodically corrects for a spatial conflict generated by proximate motion signals that differ in perceived speed.

Humpback whale social sounds: Sources levels and response to playback

Humpback whale ‘‘social sounds’’ appear to be used in communication when whales interact but they have received little study in comparison to the song. During experiments as part of the Humpback whale Acoustics Research Collaboration (HARC), whales migrating past the study site on the east coast of Australia produced a wide range of social sounds. Whales were tracked visually using a theodolite and singers were tracked acoustically using an array of five widely spaced hydrophones. Source levels of social sounds were calculated from the received level of the sounds, corrected for measured propagation loss. Playbacks of social sounds were made using a J11 transducer and the consequent reactions were recorded in terms of the change in direction of the migrating whales in relation to the playback position. In one playback, a DTAG was place on a female with calf. Playback of social sounds resulted in significant changes in the course of the migrating whales, in some cases towards the transducer while in others it was away from the transducer. From the estimates of source levels it is possible to assess the effectiveness of the playback and the range of influence of social sounds. [Work supported by ONR and DSTO.]