Bottlenose dolphins double their known range!

Dr Jean Paul Roux from the Ministry of Fisheries, who we collaborate with down in Luderitz sent me some photos they captured from shore in April of a group of bottlenose dolphins in Guano Bay (the main Heaviside's dolphin concentration area in Luderitz).

Although they occasionally see bottlenose dolphins down there, they tended to be very poorly marked (undistinctive) animals, and have always been assumed to belong to the offshore stock of bottlenose dolphins (which live in the open ocean off the continental shelf, and don't mix with the local population). The Walvis Bay population has a known range from Sandwich Harbour to Cape Cross (only about ~250km along shore), but with observer effort very low north and south of these points, we assumed they probably did range a bit further than that, there was just no one there to see them.

So this sighting was really exciting as we now have photographic proof of 'our' population of bottlenose dolphins in Luderitz, about 400km south of the known limit of their range! There were about 12 animals, several well marked ones including some of those tagged in the lagoon in 2009 and some of the mother-calf pairs.

We'll be back in Walvis Bay at the beginning of June to work all of June and July and plan to spend some more time in Luderitz in August. This will give us a chance to see if these animals were simply on a summer holiday trip and have come back to Walvis Bay, or if they have 'permanently' emigrated.

Slow on the updates recently. We wrapped up the season in Walvis Bay and left town on the 26th March as I had to give a talk up in Windhoek at UNam. I've never been there before, it's quite a small university compared to Pretoria or UCT, but a nice campus. The talk went well, there was small, but interested crowd who asked lots of questions, which is always nice.

Then moved on down to Luderitz to go service the hydrophones down there and collect some skin samples for analysis. I couldn't have done it without the help of Jean Paul Roux at the Ministry of Fisheries. We took out their research ship the Anichab (actually it's "!Anichab", but apparently if you mispronounce the initial click represented by "!", you turn it into a rather rude word, so most folk err on the side of the English pronounciation and just start with the A...). It was a good few days (although pretty windy the whole time), and great having a whole ship and good crew to help with everything. Hauling the hydrophone moorings is a pleasure with a winch, and we got them cleaned up and put back in in no time. I put down another hydrophone just at the northern edge of the Lighthouse bay, to replace the one in Guano Bay that is still AWOL. Biopsying was slow work as the weather didn't play along and the dolphins weren't as super friendly as they usually are in Luderitz, but we got there in the end.

Exciting sighting of the week - 2 minke whales! Apparently there are two or three in the bay which have been around and seen on a weekly basis since December by Heiko Metzger (Zeepard Tours). I've put in a few photos below of hauling and cleaning the hydrophones and the minke whales as seen from the ship and one of JP's pics of me and the !Anichab crew out in the little dinghy trying to get biopsies.

More exciting news - JP just emailed me the other day to say that a few bottlenose dolphins had been spotted in the bay and they all had large distinctive markings. The Walvis Bay population isn't supposed to range so far south (it's ~400km from Walvis), and bottlenose dolphins that have been seen there previously are thought to be vagrants from the offshore populations. However...photo ID will tell and hopefully the Luderitz locals can get us some usable photos.. i'll keep you informed.

Busy times here. We were out to sea almost everyday last week and had a great run of good dolphins and good weather. Luckily(?) that's turned now and it's been quiet and rather choppy out there the last two days, so we're taking today off to catch up a little. Season is drawing to a close and there's still lots to do and summarise.

The good news - we have twice seen the injured dolphin since the original report a few blog posts ago. He ('it' really as we don't know it's sex) still bowrides the boat, but most importantly is healing amazingly well. If you click on the images it opens a slightly larger version. Compare the two photos below to the open wounds of the original photos. I'm really quite astounded at how well these wounds have healed.

I sent an email around to all the tour operators about this sighting and I think it really brought it home to them that as the people out there every day, the responsibility for the animals lies with them. They have all been really good about not reverse bowriding with the dolphins and letting them determine the space use a little more.

Jeff Slater from Cape Town has joined me up here for the month to help out on the boat with driving and taking photos. Jeff is considering a career in marine biology and I'm doing my best to show him both sides of the coin - the fun side on the water, and the real work which involves sitting behind a computer for hours on end processing data, writing grant applications and updating the blog. I really ought to put up more pictures of empty seas on misty days, freezing cold mornings and dimly lit offices with flickering computer monitors - just to give a more rounded view of what we do out here :) I'd also roped in Edith Mertz, to help me out for a few weeks. Edith is a Master's student of mine who's investigating the interactions between cetaceans and a fin-fish farm that is being developed in Mossel Bay. It's something we also touch on here in Namibia here there are a large number of oyster farms in the bay. Now that we have four seasons of spatial data from Walvis, it's really interesting looking at the variation in habitat use between seasons, and what the implications of that are for coastal development or trying to make restricted or protected areas. Edith's work is described on the site below:

http://www.oceans-research.com/marinescienceprojects/mosselbaycetaceans.html

Time for an update - we've a few really nice days recently. Loads of sunshine, flat calm and lots of dolphins. Managed to see a leather back turtle, 2 sunfish (Mola) and multiple Heaviside's dolphins groups the other day during a 10 minute period.

Had a resighting today of another Heaviside's form the 2008 catalogue which is great. We also saw the wounded dolphin again (see entry below for details), he came to bowride brielfy and the wound looked a little more healed (paler, less raw) but i only managed to get a shot of it under water.

Had a great day with two groups of bottlenose today (both of 3 animals) and loads of friendly Heaviside's. we were pretty much with dolphins solidly between 8:00 and 12:30 today. One of the bottlenose dolphins caught a massive fish, i think it was a springer (type of large mullet) and swam around with it for ages.

Hydrophone deployed at Sandwich Harbour!

We’ve been wanting to do some work down in Sandwich Harbour for a while now and eventually managed to get there today by boat. Sandwich Harbour is a similar, but shallower embayment ~50km south of Walvis Bay. Although it used to be deep enough for ships to sail into it and refill their water supplies, the movement of the dunes and erosion by the sea has made the whole bay much shallower, the mouth narrower and dug considerably into the dunes which lie alongside the sea. To illustrate how dynamic an environment these sandy coastlines are here – the GPS map was WAY off down there and indicated us being on land on several occasions.

The attraction of this area from our point of view is that there is almost NO human activity in the area (barring a bit of light fishing and the occasional weekend boat), which makes it a very interesting comparative site to Walvis Bay with its harbour, tourism and aquaculture – are the animals using the area differently down there? We hope that a month of a hydrophone logging the presence and absence of the dolphins in the area will gives us some indication of their habitat use patterns in the absence of human activity.

We looked at various options to get down there including towing the boat down the beach, borrowing a smaller boat to tow or using a bigger boat which we could stay on. I briefly flirted with the idea of buying our own catamaran, but then remembered I’m a scientist not an internet millionaire. So in the end, the quickest and easiest way was to drive down the coast with Nanuuq and back. It’s a very long way (the GPS track showed 84nm total for the day – I won’t tell you how much fuel we used, it makes me feel a little bit sick) along a very exposed and lonely section of coastline. We had really hoped to stay over there and send fuel down by car and then be able to work for two days in the area to allow us to do some more exploring and photo-ID work, before heading back up and thus make the most of the fuel use. Unfortunately the Ministry of Environment (MET) wouldn’t give us a permit to stay over, merely to enter the area (it is part of the Namib Naukluft National Park).

So with the wind picking up quite strongly every afternoon here, we were on a pretty tight time schedule and had to leave Walvis at 6am and head straight down there only recording dolphins as we passed. But the good news is that the weather held out all day, we got the hydrophone in the water (red star on map) and back home safely before the wind picked up! Not many dolphins to report unfortunately, a few small groups of Heaviside’s in the mid-section of the trip (the blue dots on the map) but a good day all round. The white bar on the map indicates 50km

Moving house tomorrow and then back on the water on the weekend.

While out yesterday on a fairly average misty, windy day, we encountered a Heaviside’s dolphin with clear propeller wounds down the length of its body. As you can see from the photos below, it was quite a horrific looking injury. However, the animal was remarkably unafraid of the boat and would still occasionally bow ride our boat and we hope it will make a full recovery over time.

Why dolphins bow ride is not fully understood, but simple ‘play’ behaviour is the most likely reason. It's occurrence is clearly affected by the behavioural state (or mood) of the animal, as well fed or socializing animals bow ride far more keenly than those which are busy hunting or resting. Dolphins ride swell in the open ocean and surf near beaches and they will even ride the bow wave of large whales. The behaviour may be related to the practice of swimming in their mothers slipstream as calves. Heaviside’s dolphins, when in the mood, are particularly avid bowriders. Heaviside’s dolphins will even ride a boat going in reverse, when they swim very, very close to the engines. The keenness with which some species and individuals bow ride can be likened to dogs chasing cars. And it is the role of the boat skipper to bear in mind that just because an animal will react in a certain way to a boat, it is not necessarily a good practice to do it (would you throw stones at elephants to make them charge you?).

The high amount of boat traffic at Pelican Point has always been a concern to local conservation organizations and understanding the potential impact of this traffic was one of the motivating factors behind the development of the Namibian Dolphin Project. Sightings like this re-enforce the need for protocol compliance and the application of common sense and environmental responsibility while interacting with these fantastic animals.

Beach survey to Cape Cross

by Michelle Wcisel

“There is a sufficiency in the world for man's need but not for man's greed.” ~Mohandas K. Gandhi (Warning: Some readers may find the pictures in this blog post disturbing).

Yesterday, we took a shore-side drive to Cape Cross to scope out potential launch sites with the hope of expanding our coverage of the coast to the north. However the tone of the trip quickly changed to a beach scavenging expedition as we learned the truth behind the “Skeleton Coast.” We found countless Cape fur seal skeletons, a few leatherback turtle carapaces that had been bleached in the sun, dozens of stranded shore birds, and four spotted gully sharks. The majority of the carcases were there due to natural causes, but every shark we found had been hooked and carelessly cut from the line.

When your career is in a biological science, especially one that is based in field research, you are exposed to life and death daily. You come to understand that cycle as an integral piece of a healthy ecosystem, and seeing a natural death of an animal changes from a mournful moment to solemn recognition of a bigger process in action. But, when you come upon an animal that has had its life taken by a hook, or a piece of line that cuts through its body, or a plastic bag lodged in its throat, you never stop feeling infuriated.

The first spotted gully shark had been killed within the hour we found it. It was a female, her gills were bright red and her body was still cold to the touch (cold because she had just been in the cool water, if she had been on the beach for awhile, her skin would have been hot from the sun – like the other three sharks we found). The line had cut through the corner of her jaw and it was obvious she had given the fishermen a “lekker fight” since the tension of the line had worked a massive wound into the side of her face. Out of curiosity, we collected her to do a full autopsy to further determine her cause of death, but were not expecting to find that the majority of this 1.55m shark’s body cavity was uterus. She was carrying 8 pups, 4 female and 4 male, all around 33cm in length. We eventually found the hook, which had punctured through her oesophagus, worked into her pericardial cavity, and pierced the left side of her heart. It is impossible to tell which of these injuries killed her first.

A mass loss of life like this feels overwhelming when you extrapolate it to all the world’s beaches, especially when you consider how this pales in significance to some of the horrors happening in the offshore fishing fleets. It is legal in Namibia to catch spotted gully sharks and they are classified on one of the lowest ranks by the IUCN Red data list as “near threatened”. However, it is important to recognize this type of blatant waste in order to inspire more research, more students, and further grasp the sense of urgency our oceans are silently suffering. If nothing else, the death of those sharks inspired a blog, maybe a few conversations, and perhaps some of you readers got to see images that are unfortunately all too commonplace to us in marine biology.