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Marine Mammal Program
1. Introduction

 

The Kisite-Mpunguti Marine National Park is situated on Kenya’s south coast off Shimoni, lying just south of Wasini Island, near the Tanzanian border. The Kisite MPA covers approximately 11km2 while the Mpunguti marine reserve covers approximately 28km2. The marine park boasts incredible snorkelling and diving as well as being one of the most likely areas for spotting cetaceans. Therefore it is not surprising that this area
is a very popular tourist destination bringing in vital revenue for local businesses and people.

Kilifi is situated on the north coast of Kenya approximately 55km north of Mombasa city. It possesses one of the largest creeks along the Kenyan coast, comprising a number of various biotopes including mangroves, fringing reefs and seagrass beds. However, regardless of these various biotope systems, this area is unprotected and is a very popular ring/seine net fishing ground for local people. Cetaceans have often been spotted along this part of the coastline, yet no research has been conducted on this area.

2. Aims

 

The aim of this project is to: 1) To create a long term, extensive and comprehensive data set on cetacean movement, behavior and ecology; 2) Create an acoustic sound library of cetaceans to accompany cetacean sighting data for use in monitoring.

3. Cetacean Morphology

 

Parts of Dolphin Used in Identification
In this program it is very important for you to be able to distinguish between the SIX common species of dolphin in Kenya and one species of baleen whale (humpback whale). The following section gives you the basic identification characteristics; however it is very important that you learn as much as possible before arriving as this will significantly help you in the field.

ORDER CETACEA

SUBORDER ODONTOCETI (TOOTHED WHALES)

This suborder contains the whales and dolphins with a single blow hole and very obvious teeth for catching prey. Currently there is estimated to be 66 species worldwide in this suborder.

Common dolphin (Delphinus delphis)

  • Calves up to 80cm, Adults up to 2.3m
  • Body slender and robust
  • Long sickle shaped dorsal fin and narrow flukes
  • Body is black on top from the beak to midway between dorsal fin and flukes
  • Distinctive hour-glass pattern of yellow brown and grey on the sides of the body

Common dolphins are often found schooling in mixed groups (usually with spinner dolphins – see below). They may bow ride and jump, but do not spin. Distributed worldwide from deep oceans to shallow coastal areas.

Humpback dolphin (Sousa chinensis)

  • Calves up to 90cm; Adults up to 2.8m
  • Very distinctive dolphin with a long and slender back
  • Characteristic thickened ridge on middle of back
  • Small pointed dorsal fin
  • Dark grey to black upper body fading into off white underneath

Usually found in small groups and are fairly shy, but may occasionally bow ride. They inhabit shallow coastal areas and are distributed in the Indian and Pacific Oceans.

Bottlenose Dolphin
Bottlenose dolphin (Tursiops aduncus)

  • Calves up to 100cm; Adults up to 4m
  • By far the largest of dolphin species
  • Long robust body with small, pointed pectoral fins and tail fluke
  • The beak is short and stout with a distinctive crease where it meets the melon
  • Body is grey above with a white and spotted underside

Bottlenose dolphins are extremely inquisitive and often bow ride with boats. They are highly acrobatic and are often seen ‘showing off’ near boats. They are found in coastal areas and are distributed from the Western Indian Ocean to Red Sea and Western Pacific.

Spinner Dolphin
Spinner dolphin (Stenella longirostris)

  • Calves up to 80cm; Adults up to 2.3m
  • Slender body with very long beak
  • Long pointed pectoral fins and tail fluke
  • Grey upper body fading to pale grey on flanks to white underneath
  • Dark patch encircles the eye which extends to the tip of the beak

Spinner dolphins are incredibly acrobatic and very playful. They frequently bow ride with boats and are so named for their distinctive ‘spinning’ through the air when they jump. They are incredibly social and usually school in mixed species groups. They can be spotted in very large groups of numbers reaching up to 1000! They are usually ocean going pelagic species; however they can be spotted quiet close inshore and are found worldwide in the tropics.

Spotted Dolphin
Spotted dolphin (Stenella attenuate)

  • Calves up to 80cm; Adults up to 2.3m
  • Curved robust dorsal fin and long pectoral fins
  • Distinctive ‘keel’ on underside of body towards the end of the tail stock
  • Long white beak with white ‘lips’
  • Body is dark grey with numerous white spots particularly on flanks and lower parts (adults only)

Spotted dolphins are far less acrobatic and rarely bow ride making them difficult to spot. They are distributed worldwide in the tropics and are also found much further offshore and rarely come in close making them even more difficult to study/spot.

Risso Dolphin
Risso’s dolphin (Grampus griseus)

  • Calves up to 150cm; Adults up to 4m
  • Very distinctive dolphin with characteristic dome shaped melon with a V shaped groove down
    forehead
  • Lacks an obvious beak
  • Body surface is mottled whitish-grey and is covered in obvious scratches and markings
  • Very tall, slightly curved dorsal fin in the middle of back
  • Long, slender pectoral fins with tail fluke curved and serrated

Risso’s dolphin are very difficult to spot in Kenyan waters as they are rarely acrobatic and rarely breach the surface long enough to identify. They also travel in very small numbers. They are distributed worldwide in warm waters and are found in both inshore and offshore habitats.

SUBORDER MYSTICETI (BALEEN WHALES)

These are the large filter-feeding whales with 2 blow holes. They all have sieve-like plates (baleen) that are used in filter-feeding of plankton. Most of the 11 species in this suborder are highly migratory.

Humpback Whale
Humpback Whale (Megaptera novaengliae)

  • Calves up to 5m; Adults up to 18m
  • Rounded body with massive head
  • Long pectoral fins which are broadly serrated on the leading edge
  • Tail fluke has white patches serrated on the trailing edge
  • Up to 30 distinctive grooves on throat
  • Upper jaw has many (up to 400) blackish brown baleen plates on each side
  • Top is dark grey to black with underside grooves white
  • Characteristic humped back with tail flukes visible on diving

Humpback whales are predominantly open ocean pelagic mammals, but do come in quite close to shore on occasion. They are distributed worldwide travelling down to warmer waters in the European summer months (May- September). Despite their vulnerable status, they are common in the Western Indian Ocean and off the coast off Kenya during the months between June and November.

4. Methodology

 

4.1. Cetacean Sighting

A random stratified approach will be used whereby pre-planned routes will be methodically spaced, but randomly placed, to cover the study area as well as different habitat ranges and depth contours. The research vessel will serve as a platform in order for the observers to spot and record species type, number of individuals, GPS location and to take photographs for permanent record and photo-identification. Photo-ID’s are incredibly useful conservation wise, as in effect they are the photo equivalent of tagging and can, for example, be used to track the movements of a single individual dolphin. This is done via examining good quality photos identifying natural markings particular to that
one individual dolphin. Particular markings include scars, and colouration as well as dorsal fin outline. Furthermore the photo-ID method is used in population abundance estimates using what is termed as ‘mark-recapture’ technique which is vital in monitoring studies.

Alternatively shipboard visual surveys will be conducted on pre-selected, spaced transects that will encompass the full study area and depth contours, thus covering different habitat ranges. Weather permitting the research vessel will follow these transects while observers will spot cetacean activity and record the sighting time, sighting angle to the transect, distance to transect, group size, and any human activities around the dolphins (e.g. fishing). This method is very intensive, also requiring correction factors, and is also better suited to calm seas so may not be used.

4.2. Underwater Acoustic Recording

Animal bioacoustics is a fascinating area of scientific research. So far this has not been conducted on marine mammals in Kenya and therefore opens up a brand new avenue of research questions and survey work.

We will place underwater hydrophones into the water column once dolphins/whales are spotted by the observers. The sounds created will be recorded while the siting data, as per the siting protocol (section 4.1.), is simultaneously recorded. The sound data will be analysed back at the lab onshore.

The computer software will be able to display sound in a spectrogram time series as well as detect distance, bearing angle and signature of specific species of marine mammal. The bioacoustic data will add to the siting data in that we will be potentially be able to match specific sounds signatures to individuals within a pod. This is especially useful for certain species that are hard to photograph/spot, such as humpback dolphin or Risso’s dolphin, as they spend majority of their time underwater. Furthermore we may also be able to determine behavioural characteristics via certain sounds, such as feeding, mating, or travelling for example.

Recommended Reading

  • Cawardine, M. Whales, Dolphins & Porpoises. Dorling Kindersley Handbooks
  • Buckland, S.T., Anderson, D.R., Burnham, K.P., Laake, J.L. Distance Sampling: Estimating Abundance of Biological Populations.446pp. Springer
  • Jefferson., & Jarret, B. Marine Mammals of the World: A Comprehensive Guide to Their Identification. 592pp. Academic Press
  • Whitlow, W.L., & Hastings, M.C. Principles of Marine Bioacoustics. 680pp. Springer