A windy start to the first field season

by Tim Hunt

​

The North West Cape Dolphin Research Project (NWCDRP) has begun, kicking off a couple of months ago in late May 2013.

The aim of the project over the coming years is to determine the population size, habitat use and social structure of Australian humpback dolphins (Sousa chinensis) around the North West Cape, Western Australia. The dolphin research team (aka “Team Sousa”) is based here in Exmouth, Western Australia for the winter months (May-October), exploring the inshore waters of the World Heritage Listed Ningaloo Marine Park and Exmouth Gulf around the tip of the North West Cape. Very little is known about humpback dolphins in Western Australia and as such there is not enough information available to properly assess the conservation status of the species. From the small amount we do know about the species in Australia, it appears that humpback dolphins live in small, geographically and genetically isolated populations of 50-100 animals in shallow, tropical coastal environments (<15 m water depth). These factors, along with a low reproductive rate (calves born only every few years) suggest that this species is vulnerable to localised impacts such as coastal development, and therefore localised extinction from an area is a real possibility if not managed properly. Information gathered on humpback dolphins (and bottlenose dolphins) during this project is important given it will help inform the conservation and management of this data poor species in waters around the North West Cape from potential current and future impacts, and aid in a better understanding of the species in Western Australia and nationally.

The NWCDRP is led by Dr. Guido J. Parra at the Cetacean Ecology, Behaviour and Evolution Lab (CEBEL)) Flinders University, South Australia. CEBEL PhD Candidate Tim Hunt is the primary researcher on the project. Also involved in the project and supervising Tim are Associate Professor Lars Bejder and Mr Simon Allen from the Murdoch University Cetacean Research Unit (MUCRU), Western Australia. The project is funded by the Australian Marine Mammal Centre Grants Scheme and supported by the Western Australian Government Department of Parks and Wildlife (formerly Department of Environment and Conservation).

Since arriving in May the weather and the winds in the Exmouth region have been ‘abnormal’ to say the least. In order to conduct dolphin surveys it is preferable if the wind is 10 knots (18 km/h) or less, and a sea state without white caps. Any windier than this and it becomes quite difficult to spot dolphins. Even if you were to see dolphins it’s quite tricky to photograph them with the boat bouncing around, and you of course risk getting your camera splashed with seawater. Digital camera equipment and salt do not mix! The two months we’ve been here we’ve had a couple of storms and experienced almost 200mm of rain. This doesn’t sound like much, but considering the region we’re in is relatively dry for the tropics, it’s still technically the ‘dry season’ (i.e. non-cyclone season) and the average annual rainfall of Exmouth is less than 300mm, I think ‘abnormal’ is an appropriate word to describe the weather here of late! Wind over the past couple of months has averaged well above 10 knots and as such we’ve had a number of days off in a row off the water. Nonetheless, although it has been an unusually windy start to the field season, the days we have managed to get out we’ve seen dolphins every time, and there are certainly plenty about which makes for lots of data and solid research.

In order to collect data and systematically cover the study area, we have 2 x 93km transect lines that zig zag their way from Exmouth, north around the tip and south to Mangrove Bay on the Ningaloo Reef side of the Cape. As we travel along these transects at slow speed (~10 km/h) we search for dolphins. When we spot dolphins we observe behaviour, record group size and composition (i.e. number of adults, juveniles and calves,) take photographs of their dorsal fins (in order to identify each individual), and record environmental variables (i.e. water depth, water temperature, salinity, pH, and turbidity) in the area the dolphins are sighted and throughout the study area. We will repeat these transects as many times as possible throughout each field season (May-Oct) in order to comprehensively cover the inshore waters of the North West Cape with the aim to determine the density and population size of dolphins in the area and how these animals are using different areas around the NWC. As indicated above, the focus species for this research project is humpback dolphins, however the region is also home to bottlenose dolphins (Tursiops aduncus) which we also collect information on. Interestingly, the two species have often been observed socialising in mixed species groups. During these events we will often observe the humpback dolphins exhibiting a behaviour that can best be described as “pirouetting” (where the animal is vertical in the water, its head and rostrum protruding from the surface and the animal will spin with its pectoral fins outstretched). It’s only the humpback dolphins that appear to be doing this while the bottlenose dolphins roll over and around the humpbacks. It certainly appears to be quite “frisky” behaviour between the two species.

Since commencing dolphin surveys on 23 May 2013, Team Sousa have been on the water 23 days (or part thereof due to windy weather). An identification catalogue for each species of dolphin sighted within the study area has been developed and to date, a total of 43 humpback dolphins have been identified (not including calves). A large proportion of these animals have been sighted more than once on separate days, suggesting there is a degree of residency of the dolphins to the NWC. Over 50 bottlenose dolphins have been identified thus far (not including calves), a large proportion of which have also been sighted more than once on separate days, again suggesting a degree of residency in the area. These findings are of course only preliminary, but over time as we collect more data throughout this field season and the coming field seasons, we will be able to work out how many animals are regularly sighted and thus determine population size. We can also work out which animals appear to associate with each other on a more than regular basis, and then by collecting genetic material in addition to photographic material, we will be able to paint a picture as to the social structure of the dolphins in the area (i.e. are those groups travelling together related, what is the sex of the individuals that are regularly seen together etc). Social structure in bottlenose dolphins is quite well studied and understood, but in the case of humpback dolphins, this is something that has not been well studied.

Team Sousa work hard both on and off the water. If the weather is good we can sometimes be out all day on the water (7am-5pm), in the heat, constantly on the lookout for dolphins and regularly collecting data. We have to work together as a team and communicate well in order for things to run smoothly when out on the water. A full day’s worth of data sheets and photographs means almost as long in the ‘office’ downloading and entering data onto the computer, and processing photos ready for matching. In addition to data entering and processing, all the equipment needs to be cleaned, boat fuelled and rinsed, and food prepped ready for the next day of fieldwork. Field work is quite involved, but very rewarding when you’re out there on the water studying dolphins, knowing that the information you are collecting will be used to better understand the species and used to better inform their conservation and management, particularly in an area with the potential to undergo increased development and exploration in the near future.

Team Sousa is of an international flavour, and to date has consisted of Tim Hunt (Australia), Dr. Guido Parra (Australia via Colombia), Katharina Peters (Australia via Germany), Lauren Connor (USA) and Katy Gavrilchuk (Canada). Tim would very much like to thank Team Sousa thus far for their efforts both on and off the water in getting this project ‘fine-tuned’ and running smoothly.

Conducting fieldwork in the waters of the World-Heritage Listed Ningaloo Marine Park, with the red cliffs of Cape Range National Park as a backdrop is, for lack of a better word, amazing. There are more than just dolphins in this beautiful part of the world, and we’ve managed to capture a few snapshots of humpback whales, manta rays, marine turtles, dugongs, and even a whale shark. Our GoPro3 has certainly been put to work under the water and we’ve been fortunate enough to capture images of these wondrous animals as they go about their daily business under the surfaces of this picturesque turquoise ocean.

Team Sousa would like to thank the staff at the Department of Parks and Wildlife (DPaW) - Exmouth Office (formerly Department of Environment and Conservation or DEC) for their support this field season thus far. DPaW have shared their knowledge of the area which was imperative in finalising our transect lines. Their marine mammal sighting data has also given us an insight to areas for possible future investigation outside our current study site.

Team Sousa would also like to thank John Totterdell (MIRG Australia) and the research team from the NOAA Southwest Fisheries Science Centre USA (Robert Pitman, Lisa Ballance and Holly Fearnbach) for sharing their dolphin sighting information with us while they were in Exmouth over the past month searching for killer whales off the Ningaloo Coast. Unfortunately we can’t be everywhere at once so getting dolphin sighting information in areas where we are not is extremely valuable.

That pretty much wraps up the first blog for this season. The team is certainly hoping for an improvement in the weather for the next three months and is very much looking forward to some great days on the water in this beautiful part of Australia. It is anticipated a blog will be posted once a month, so expect a few stories and a lot more pictures from our experiences around the North West Cape.

Now let’s go find some dolphins!

See you on the water!