Report on Bottlenose Dolphins (Tursiops truncatus)

The Bottlenose Dolphins (Tursiops truncatus) are residents of the Strait of Gibraltar, roaming in ever-smaller pods over time. They show their tricks, like jumps, mainly at the beginning of the summer season.

Position Große Tümmler 1999–2015
Positions of Bottlenose Dolphins from 1999 to 2015

Our photo identification of Bottlenose Dolphins proves that this species is resident in the Strait of Gibraltar. However, there is now a steady decline in average group size. This could be due to a change in group dynamics or the morbillivirus epidemic. The population of Bottlenose Dolphins in the Strait of Gibraltar did not seem to be affected by this virus at first, but perhaps not as severely.

We observe the playful behaviour typical of Bottlenose Dolphins especially at the beginning of the season. According to our records, however, this behaviour decreases continuously throughout the season. It could be a natural periodicity depending on the mating season, leading to the Bottlenose Dolphins becoming more socialized in spring. Or maybe they have got enough of whale watchers towards the end of the season.

Keydata from annual reports

2004

  • Photo ID of Bottlenose Dolphins suggests that also this species is resident in the Strait of Gibraltar

2005

  • Photo ID demonstrates that this species is resident in the Strait of Gibraltar. In the Strait we have four resident and six migrating cetaceans

2006

  • Largest pod: about 120 animals
  • It looks like their population is growing

2007

  • Largest pod: about 200 animals
  • It looks like a healthy population

2008

  • Largest pod: about 200 animals

2009

  • Bottlenose Dolphins seem not to be affected by the morbillivirus epidemic as the Pilot Whales are
  • Largest pod: 120 animals
    (The largest pods of Bottlenose Dolphins and Pilot Whales were only half as large as those of the season 2008)

2010

  • Sighted in "normal" numbers until middle of season
  • Started to vanish after midseason, which is reflected in an overall 40 % drop of sightings compared to the season of 2009
  • Largest pod: 200 animals
  • Only once sighting of a large pod of 110 dolphins in the second half of the season, in September

2011

  • More dolphins in the first half of the season
  • Largest pods with 100+15 and 120+20 adults+calves in June

2012

  • More dolphins in the first half of the season (until July)
  • In July: pod of 65+15 adults + calves
    (Only half the size than the largest one of the last season)

2013

  • More dolphins at the beginning of the season (April, May)
  • April: pod with 130+20 adults+calves
  • July: pod of 88 animals
  • October: pod of 70 animals
  • Rest of the season: pods of less than 50 animals
  • Population seems to be stable at first in the Strait of Gibraltar

2014

  • Larger pods with 50 – 95 animals from March to September
  • Largest pod: 80+15 adults+calves on August 3rd
  • Most babies and newborn in July, August and September (until late summer, same as Pilot Whales)
  • Average pod size: 20 animals (2013 it was 22 -; until 2007 still 24,5 animals)

2015

  • Large pods of 51 to 88 animals from June to October
  • Largest pod of 101 animals (inlcuding 10 calves and 1 newborn) on April 19th
  • Calves throughout the summer
  • Most newborn from July to September
  • Average pod size: 16 animals

2016

  • Larger pods of 50 and more animals from May to August
  • Largest pod of 170 animals on Mai 7th
  • August 29th: 155 animals
  • Calves throughout the summer, most from May to July
  • Most newborn in August and September
  • Average pod size: 15,8 animals

2017

  • Larger pods of more than 50 animals from April to September
  • Largest pods of 100 and 120 animals on June 15th and August 2nd respectively
  • Calves throughout the summer, most of them in April and May
  • Only 8 newborn from April to September, 3 of them in July
  • Overall, the newborn appeared one month earlier than those of the last season
  • Average pod size: 12 animals

2018

  • Larger pods of 40 and more Bottlenose Dolphins in July, August and October
  • Largest pod of 56 animals at August 9th
  • Average pod size: 12 animals (constant decrease since 1999)
  • Calves throughout the season, most of them in August
    (normally we observe most of them from April to June)
  • 46 sightings of newborn from May to November

For firmm reports sorted by years (in German) check out firmm-education.