A preliminary study of the movement patterns of false killer whales (Pseudorca crassidens) in coastal and pelagic waters of the Northern Territory, Australia

Abstract

The false killer whale (Pseudorca crassidens) is regarded as Data Deficient globally and in Australia. In most parts of its range, there is little information on its social behaviour, dispersal or ecology. The present study is the first assessment of its movement patterns in Australian waters, on the basis of satellite tracking of four individuals, in the Arafura and Timor Seas from late March to early July 2014. When initially tagged, the four individuals occurred in a single group; they then showed generally similar movement patterns and regularly re-associated. Total distance travelled by tagged individuals ranged from 5161km (over a 54-day period) to 7577km (104 days). Distance from land varied from 100m to 188km (median distance 24km). Individual minimum convex polygons covered an area of 72368 to 86252km2, with a total overlap of 64038km2. Water depths varied from 0.3 to 118m (median 36m). In total, 15% of records were in waters shallower than 10m, and 26% of records were within 10km of land. The present study indicated that false killer whales appear to regularly use coastal and pelagic waters in this region and, hence, should be afforded more conservation attention.

Monitoring Variation in Small Coastal Dolphin Populations: An Example from Darwin, Northern Territory, Australia

“…Currently, there is little basis for understanding coastal dolphin movement and ranging patterns in monsoonal northern Australia. Coastal dolphins may be responding to seasonal influences (Smith, 2012;Palmer et al, 2017) and spatial and temporal variation in the abundance of prey species (Silva et al, 2009;Cagnazzi et al, 2013;Parra and Cagnazzi, 2016). However, the results have highlighted that the study period (three and half years) and study area (1086 km 2 ) didn't encompass the whole ranging patterns for the three species, which appears to be much larger than assumed (Silva et al, 2009;Nicholson et al, 2012;Palmer et al, 2014b;Brown et al, 2016).…”

Translocation, genetic structure and homing ability confirm geographic barriers disrupt saltwater crocodile movement and dispersal

“…There are some significant deep channels on the eastern side (<164 m), and large tides (<8 m) [37] combined with seasonal monsoons, in which wind strength and direction change [38], which may interfere with animal movements, perhaps through the avoidance of rough surface currents flowing against them when travelling at sea. Satellite tracking of false killer whales ( Pseudorca crassidens ) in the Cobourg Peninsula area has shown that they rarely entered the western side of the Cobourg Peninsula, into Van Diemen Gulf, despite occupying shallow (<10 m depth) waters within 10km of the coast, on the eastern side [39], which could also be related to currents.…”

Home Sweet Home? Wide-Ranging Movements of Socially Stable Resident Delphinids (Globicephala macrorhynchus)

“…Such capability is supported by the total distance travelled and/or the continuous movements monitored via satellite-linked telemetry in short-finned pilot whales off Florida (Well et al 2013) and Hawai'i (Abecassis et al 2015), as well as in other delphinid species. Examples include the related congener species, the long-finned pilot whale (G. melas) (Nawojchik et al 2003), the false killer whale (Pseudorca crassidens) (Baird et al 2012;Palmer et al 2017), the pigmy killer whale (Feresa attenuata) (Baird et al 2011), or the killer whale (Dahlheim et al 2008;Durban and Pitman 2012). Yet, none of the previous examples relate to animals with (known strong) site fidelity, contrary to what shown in our study.…”