There is an urgent need to monitor and protect the marine environment in the Greater Dyer Island area. Specifically, to date, no fine-scale long-term study has been carried out in the area concerning the distribution and behavioural patterns of cetaceans (marine mammals). The area is facing potential development and is already under impact from various forms of marine tourism. Cetacean species known to use the area include the endangered Indo-Pacific humpback dolphins (Sousa chinensis), southern right whales (Eubalaena australis), humpback whales (Megaptera novaeangliae), Bryde’s whales (Balaenoptera edeni), Indo-Pacific bottlenose dolphins (Tursiops aduncus) and common dolphins (Delphinus capensis). Many of these species are listed as either Data Deficient or Vulnerable on the IUCN list.
The area is exposed to a variety of potentially detrimental human impacts. Collecting data now is therefore important as the area is already impacted by the shark cage diving industry, boat-based whale watching, and leisure boats, as well as a potential site for an aquaculture and a nuclear power station.
The effects of aquaculture on cetaceans are not well studied. Some threats such as animals becoming entangled in anti-predator nets are clear. Many others are quite subtle and difficult to measure. Habitat loss may be one of the largest impacts of aquaculture on near-shore dolphin populations. Observations of dolphins around shellfish farms show clear patterns of avoidance and reduced usage of the farm. Loss of these key habitats could have important population level impacts for cetaceans.
Nuclear Power Station
Potential impacts of a nuclear power station include:
(1) Increased water temperature (estimated up to 12° C around outlet pipes).
(2) Increased background noise (unknown).
(3) Up to 10.07 million m³ of sediment discharged into the water column.
(4) Water intake and output (risk of animals being sucked in).
(5) Contamination (chlorine, sewer discharge during pipe cleaning and flushing).
It is not known how these impacts will affect the cetaceans in the area.
Tourism and leisure boats
The area is highly important as a recreational and tourism location. Depending on weather, the eight shark cage diving boats and two whale watching boats use the area on a daily basis. There is strong evidence showing clear behavioural changes in many species of cetacean caused by boat traffic, including horizontal avoidance, longer dives, increased speed and changes in vocalisation. More recently, longer term studies have shown that these short-term behavioural changes may accumulate into larger population-scale effects including temporary and permanent emigration of some individuals from key habitats.
This study will address the following questions:
• What is the seasonality of cetacean species using the area?
• How long do the different species of cetaceans stay in the area?
• Do different cetacean species use the area differently?
• Do certain individuals use the area more frequently than others?
• What types of behaviours are observed in the area?
• What is the seasonal pattern of the different types of behaviour?
• How vocal are the cetaceans in the area?
• What are the seasonal and diurnal patterns of vocalisation?
• Can we use these vocalisations to monitor cetacean habitat use?
The result of this study will allow us to address conservation issues relating to the development of the area including identifying key areas and times that are of maximum conservation priority. Knowledge provided by this study can be utilised in future decisions concerning the protection of the marine environment and will contribute directly to the protection of the cetacean species located in this area.
This study is the first of its kind in South Africa. The project implements the combined methods of passive acoustic monitoring, theodolite tracking and the creation of an archived long term (11 years) database of opportunistic observation data from the Dyer Island Cruises whale watching vessel.
This study will use three main methods:
• Passive Acoustic Monitoring (PAM) using four bottom mounted DSG-Oceans (Loggerhead Systems).
• Land-based tracking of cetaceans using a surveyor’s theodolite (a precision instrument for measuring angles in the horizontal and vertical planes).
• Unique dataset of 11 years of observations from a commercial whale watching boat.
Passive Acoustic Monitoring
Cetaceans are highly vocal animals, relying on sound for orientation and communication. PAM enables the researchers to monitor an area acoustically. Cetaceans spend the majority of their time submerged. Thus, passive acoustic techniques have the advantage over visual methods in being able to detect animals with substantial dive times, at night, and in poor weather.
Detection rates of cetaceans using acoustic methods can be five to eight times higher than visual techniques. When combined, visual and acoustic survey methods maximise the detection probability of marine mammals.
Four specialised acoustics recorders will be mounted on the sea floor recording vocalisations and background noise in the study area to indicate the presence/absence of animals. The acoustic recorders are being deployed on the sea floor from June 2011 to June 2012, recording for one to two months at a time. Two are in two bay areas, Pearly Beach and Franskraal, which enables the comparison of the two areas.
The maximum frequency of the acoustics recorder is up to 80 kHz, which is ideal for baleen whales as well as dolphins. Even if the dolphins can produce sounds which are well above 40 kHz (echolocation sounds) they also produce whistles and pulsed calls that are below or contain frequencies below 40 kHz.
Baleen whales use low-frequency sounds well below 1 kHz. The sound production of the southern right whales off the South African coast has not yet been intensively studied. However studies from Argentina show that the sounds of the southern right whales are concentrated in the frequency range from 50 to 500Hz.
A theodolite is being used in combination with the four recorders, as not all individual cetaceans vocalise. The theodolite is land based and is used to track the whales and dolphins. Data is collected during daylight hours from two main observation stations: Pearly Beach and the Franskraal Mountain, on an alternate schedule. Each shift consists of three observers: one skilled observer and volunteers from the Dyer Island Conservation Trust volunteer programme, as well as local students. Binoculars and the naked eye will be used during all daylight hours between 30 minutes after sunrise to 30 minutes before sunset. Once seen, groups of animals will be tracked spatially using a surveyor’s theodolite and their behaviour observed with a 30X magnification spotting telescope.
Gradually as the calves are getting larger (both longer and thicker) – their mothers are getting thinner. The mothers do not feed while they are here off the South African coast, but sustain themselves from their thick layer of blubber, which they build up while feeding in the Sub-Antarctic waters from January to May.
The southern right whale mother and calf pairs are ruling the bay at the moment! Some days we have had more than 30 pairs in the bay. They mainly spend time travelling slowly along kelp beds, relaxed, rolling, and logging in the same place. The calves are by far the most active and often breach and play around the mother. Maria has been tracking the detailed behaviour of the mother and calves, and they are spending lots of time travelling, milling, or being submerged. We have had at least five brindle calves frequenting the area. Since most of them have very distinct markings we were able to tell them apart.
We encountered dolphins on two occasions. A small group of indo-pacific humpback dolphins had a feast where they were so active that the fish were thrown into the air. Also, the indo-pacific bottlenose dolphins visited the bay and spent almost two hours surfing the waves.
The annual aerial survey of southern right whales off the South African coasts also took place in October. It was the 34th time that the Whale Unit from the Mammal Research Institute (MRI) of Pretoria have conducted the survey. Meredith Thornton, Ken Findley and Andre´ du Randt from MRI, were responsible for carrying out the survey this year. They started on the 8th of October.
The survey team takes photos of the callosity (skin growth) patterns of the mothers; each whale has a unique pattern and can be identified by this. Later the pictures will be analysed and matched to the current catalogue.
Due to the harsh weather conditions the aerial survey was only finished on the 4th of November. Normally it is completed before the end of October and takes a maximum of two weeks.
The team is looking forward to the summer and calmer weather conditions. Day by day we are seeing more and more tortoises on the roads when driving to Pearly Beach – a sure sign of summer approaching.
The theodolite tracking is running like a well-oiled machine and the team has seen sightings of humpback whales almost every week. These animals seem to have changed focus from migration to social behaviour. They spend much more time breaching and their pattern is not as predictable as the migrating humpback whales in July and August.
A new addition has permanently joined the tracking station at the water tower. A bright green snake has moved in on the rail! The team put it there to prevent the local white necked crows from ‘decorating’ the top of the tower and attracting countless tiny flies.
September was the month where the southern right whale mother-calf pairs moved into the bay while the mating groups decreased. Maria Johansen joined the team at the beginning of the month. She is here until the beginning of December conducting a small study of the interaction of the mother and calf pairs. We welcome Maria who is a dedicated biology student from the University of Copenhagen.
September marks the yearly event of the Whale Festival in Hermanus! For the team it involved public talks, manning the Dyer Island Conservation Trust stand, helping out at the children’s tent with colouring books, and exploring the festivals many attractions. The atmosphere at the festival was amazing this year, even with less than ideal weather on the Friday and Saturday – and people came from far away to celebrate the whales.
Another notable event was the four day International Aquarium Conference hosted by The Two Oceans Aquarium in Cape Town. As part of the conference the delegates went out with either Slashfin for a shark cage dive or a whale watching trip with the Whale Whisperer.
Returning to the project, the team has been spending dedicated time assessing the locations and mooring of the acoustic loggers, and we are now just waiting for consecutive calm weather days to progress further.
Perhaps the highlight of the month, however, was a flight with African Wings! A completely different and truly astonishing way to view the whales in the bay! Evan Austin took us flying for one hour allowing us to witness Dyer Island, Slashfin at sea, Kleinbaai harbour, Gansbaai and the unforgettable Walker Bay with all the whales. It is the best way to experience and understand the behaviour of the mating groups, as well as the mother and calves. Evans´ four seater Cessna 175 is ideal for the task since it does not scare the whales, and from 1000 feet we could still see every detail on the whales. Evan is an extraordinary pilot, friendly and professional, with an infectious passion for the area and the animals.
Please, if you are looking for an experience of a lifetime - now is the time to contact Evans and go and see the whales from the air!
What is that? Is it splashes from a boat? Is it the wind coming in? –NO! It is hundreds of common dolphins swimming into the bay! From the top of the water tower we can see up to 15km on a good day with clear visibility. On this unique day in August we spotted a pod of common dolphins 11 km away. The pod stretched more than one km. We alerted the whale watching boat and directed them to the sighting. They called us back shortly afterwards and reported that besides the dolphins they saw seven -eight killer whales hunting the dolphins. This is a known behaviour along South African coasts, but has never been observed in the Dyer Island area. In fact this is only the second time that killer whales have been sighted from the whale watching boat since we started in 2000. So the excitement level was high and the DVD was watched over and over again in the offices in the afternoon.
The killer whales did not catch any dolphins while the boat was there, and the pod only stayed in the area for 40 minutes. Our research boat Lwazi did try to catch up with the pod, but the dolphins had left the area and the tracking team on the tower had lost sight of them before the boat was even close to the area in which the pod was sighted by the Whale Whisperer.
Only four days after, a similar (or most likely the same) large pod of common dolphins returned to the area – this time the dolphins were feeding on sardines together with at least three Bryde´s whales. It was a spectacular sight to see these huge baleen whales shooting out of the water - in a powerful launch feed, surrounded by diving gannets and jumping common dolphins. A local sardine run! These events are rare in our area!
Southern right whales are a common sight here in August, and it has been the month where the surface active groups (SAG) returned and increased in numbers. At the beginning of the month we had four to five groups with max three individuals - reaching five to six groups with up to seven individuals at the end of the month. So more and more animals are moving in. SAG are normally related to courtship and mating behaviour.
Gradually, as we reached the end of August, we saw fewer and fewer humpback whales; by now most of them should have reached the shoreline of the Eastern Cape and Mozambique.
Anna Skinnars and Emma Fitzmaurice Vestergaard are still the backbones of the volunteer team and they make an amazing difference – conducting the theodolite tracking, entering data, analysing data, and basically pitching in whenever a helping hand is needed. They ROCK!
They also have special tasks, and Emma has been converting and filtering out all the effort data from the whale watching boat. Anna has prepared the data for the MammalMap and based on the whale watching boat data and the work of the whale research team - DICT are the first organization in Africa so submit observation data of marine mammals. See www.mammalmap.adu.org.za
A new backbone of the project is “Sir. Humphrey”. He is very reliable, adventurous, and safe addition to the team – our Land Rover Discovery TDI is making the drive to the theodolite tracking station smooth and future strandings of marine mammals will become easy accessible.
At the beginning of the month Katja went to Denmark for 10 days to work at her cooperation organisation “Statens Serum Institut”. Lots of hours were put into fundraising, writing articles, and testing the two new underwater sound stations. Doctor Michael Christiansen is an extraordinary support and help – thank you Michael.
Back in Kleinbaai the listening stations are now about to be moored at the sea floor, but with the harsh winter weather and never ending cold fronts pushing in, it has not been feasible to complete the mission yet. September is the month of the revolutionary addition of underwater sound recordings!
Breaching humpback whales, feeding groups of Indo-pacific bottlenose dolphins and southern right whales returning for the season –These are some of the amazing sightings the theodolite tracking team and the guests on the Whale Whisperer have been experiencing in June.
The theodolite tracking has been running smooth even though the winter is over us and the rough wind and rain have prevented the team to go out on several occasions –but the team is tough and in the cold mornings with frost on the lawn they wrap up in gear as if they were going to Marion Island! Since the days are shorter at the moment the team track throughout the hours of daylight if the weather permits it.
Anita Hansen (Denmark) and Anna Skinnars (Sweden) have been the dedicated volunteers in June. They have been tracking many humpback whales migrating towards their mating and nursing grounds. From the tracking data it might be possible to establish if the humpback whales are heading towards the west coast or to the east coast.
The southern right whales are back! Finally after many months where we have been longing for the sound and vision of the gentle giants. At the end of June we saw them almost on every theodolite tracking day. The amount of animals we have seen and the consistency is very similar to what is normally observed in July, so they seem to be back early and in high numbers.
After six weeks unfortunately Anita had to return to Scandinavia for other adventures, but she will return next year –she learned more about fieldwork and managing projects from being in South Africa than she ever did at the university.
Anna will stay at least until December as she says “I have to experience the wonderful South African summer after surviving the never ending cold winter!”
Besides Anna, Peet Botas (South Africa) arrived in the beginning of July. Peet is spending his winter holiday helping out as a very dedicated volunteer. They are both being trained in theodolite tracking, analysing ID-pictures of dolphins and handling large amounts of data. Both volunteers have also been out at sea with our whale watching boat “The Whale Whisperer” where they encountered the southern right whales up close. Anna said when they returned “Gosh -The size of these animals! One thing is to see them from the shore, but being next to them on the boat blows your mind!”
A trip with The Whale Whisperer is an experience for lifetime!
The theodolite tracking is going very well, and we have seen the first southern right whales, so it seems like we are going to be super busy this season! We have a few volunteers coming in to help us which will be just in time.
In September, a student will be doing a dedicated project looking further into the behaviour of whale mothers and calves. For example, she will monitor the average distance between them, which one initiates contact, and how much time they spend socialising with other mother-calf pairs. This is a spin-off from my presentation at the Danish Marine Mammal Conference which I attended in May.
Just two weeks ago I also presented at the African Marine Mammal Symposium, which we hosted at the Great White House. Around 50 participants from all over Africa were present, mainly South Africans. I presented the whale watching data, which was a huge success.
I am finalising the two first articles based on the whale-watching data at the moment. It has provided us with some very interesting trends – for example, it is clear now that the southern right whales arrive in the area in June and can be seen to have done so since 2003, as presented in our research.