Report on Pilot Whales (Globicephala melas)

The Strait of Gibraltar is home to the Common Pilot Whale (Globicephala melas). The animals are confronted with a variety of adversities in this area. Their population has constantly been declining since we started recording in 1999, today being reduced by 30-50 %. The morbillivirus epidemic of 2007, the port of Tangier Med, which was completed by 2008, and the seasonal occurrence of the Orcas are all enormous stress factors for the Pilot Whales.

Durchschnittliche Gruppengröße Grindwale 1999-2017
Average group size of Pilot Whale pods

By 2007, there were six ports directly surrounding the whale and dolphin area in the Strait of Gibraltar. The ships in the Pilot Whale area moved in the opposite direction but parallel to their swimming direction. The Pilot Whales were able to avoid the Orcas, moving to the east as far as Ceuta, especially with their calves. Since 2007 there have been ten ports in the immediate vicinity of the whales and dolphins. The ships in the eastern part of the Pilot Whale area now also move across their swimming direction. The whales can only avoid the Orcas to the east as far as Punta Cires, without getting into the regular ferry traffic between Tangier Med and Algeciras.

To the west the feeding grounds of the Pilot Whales are bordered by the submarine mountain range "Camarinal". The Orcas may provide an additional western boundary positioned similar to that of Camarinal, where the tuna fishermen work. The monthly sighting rates of Pilot Whales and Orcas from 1999-2008 show a temporal correlation between the arrival of the Orcas at the fishermen sites and the disappearance of the calves: when the first Orcas appeared in June, the sighting rate of Pilot Whale calves decreased sharply. In August, at the time of most Orca sightings, we met larger groups of Pilot Whales. A protective mechanism? In any case, the relationship between Pilot Whales and Orcas is not harmonious, but rather stressed.

The year 2008 was striking, when we frequently found adult Pilot Whales in the west end of their range, who seemed to be watching the Orcas. During the season, we also observed several times how these animals even chased the Orcas away.

Do the Pilot Whales avoid the harbour Tangier Med, moving to the west end of their range?

Positionskarte Grindwale
Positions of Pilot Whales from 1999 to 2015

2012 and 2013 were the years in which we found the Pilot Whales most westerly. In 2013, the different groups were sighted closer together. Unlike 2008, this year also saw larger groups of Pilot Whales with newborns on average more westerly than all other groups. This is remarkable and could have something to do with the port of Tangier Med. At least our data show a possible correlation between the port of Tangier Med and the movement pattern of larger groups of Pilot Whales with newborns. These groups probably are slower against the current and have therefore been sighted further east all these years. If they have changed their behaviour because of the port of Tangier Med, this port must be the worse evil; they prefer to push their newborns against the current to the west and accept the Orcas.

Together with the morbillivirus epidemic of 2007 and the fact that only 50 or 70 % of the Pilot Whales of 1999 remain, there are no rosy times ahead of them.

Keydata from annual reports

2007

  • Largest pod: 200 animals (suggests stabel growth of population of Pilot Whales in the Strait of Gibraltar)
  • Outbreak of the Morbilli-Virus epidemic (first discovered by 2008)

2008

  • Largest pod: 100 animals
  • Morbillivirus-epidemic seems to be affecting the population size

2009

  • Largest pod: 51 animals
  • In June, up to 12 calves in some pods
  • Loss of whales through the Morbillivirus-epidemic is compensated by higher birth rate

2010

  • Largest pod: 70 animals
  • Most Pilot Whale babies in July and August
  • Up to 10–18 calves in some pods spotted in August

2011

  • Largest pod: 80 animals on May 26th
  • Most of Pilot Whale babies in July and August
  • Up to 15 calves in some pods in August

2012

  • Largest pod: 60 animals on May 7th
  • Most Pilot Whale calves in April and August
  • Most babies in August, within pods of up to 20 adults

2013

  • Largest pod: 90 animals on April 25th
  • Other large pods also during spring (April, May, June), but with less than 40 animals, afterwards a constant decline of pod size. Maybe the epidemic has still not be overcome by the Pilot Whales
  • Most Pilot Whale calves from April to June
  • Largest calve-group (10 babies) in April, as part of the initially mentioned largest pod of 90 whales
  • If the current trend continues, the Pilot Whales could be vanishing from the Strait of Gibraltar by the year 2035, according to another research group

2014

  • Largest pod: 50 animals on June 7th
  • Other large pods of more than 30 animals also during June
  • Average pod size: 10 animals
  • Most Pilot Whale babies from April to August
  • Newborn even in September
  • Largest group of 12 calves in April, accompanied by only 5 adults

2015

  • Largest pod: 60 animals on April 30th
  • In May and August 2 larger pods of 55 and 35 animals repectively
  • Average pod size: 7 animals
  • Babies and newborn throughout the whole season
  • Largest group of 10 calves in April, as part of the pod of 60 Pilot Whales mentioned before

2016

  • Largest pod: 200 animals on July 30th (very unusual)
    In May, June und August a large pod of 50–70 animals respectively
  • Average pod size: 7,7 animals (somewhat larger than 2015, only a small recovery)
    Average pod size before July 30th: 8,3 animals
    Average pod size after July 30th: 6,2 animals
    Average pod size in May: 9,3 animals
  • The larger size of pods until July might be related to birth and first weeks of life of babies
  • Calves: throughout the season, in May and June most of them
  • Largest group of 20 babies in May (one month later than last two seasons), within a pod of 60 adults
  • Newborn: from March to June (with one exeption of a newborn observed in August)

2017

  • Largest pods: two groups of about 50 animals on September 25th
  • Mid of May until start of June – some pods of 20–30 animals
  • Average pod size: 6,1 animals
  • Calves throughout the season
  • No larger groups of calves; max. 3–4 calves in each pod, accompanied by 5–30 adults
  • Newborn from May to October, most of them in June and July

2018

  • Largest pod of Pilot Whales: 81 animals, including 10 calves and one newborn (March 27th)
  • Further larger pods: 50 animals (May 22nd) and 63 animals (May 28th)
    from end of March to end of June: 6 groups of 30-46 animals
    → all larger pods occurred in the first half of the season
  • Average pod size: 6.01 animals
  • Pilot Whale calves: throughout the whole season
  • Larger pods with 8-13 calves from March to May
  • Largest pod with 10 calves and 3 newborns on May 28th, accompanied by 63 adults

The larger Pilot Whale pods in the first half of the season could generally be related to the calves' births and first weeks of life. On the other hand, group size calculations until 2008 have shown that it peaked in August, when the Orcas had established themselves in the Strait of Gibraltar.

It seems that both, the birth of calves at the beginning of summer and the presence of potential predators such as Orcas at the end of summer, may have an impact on group size, resulting in two "peaks". This season, however, the Orcas were hardly seen in the range of Pilot Whales, so there was no need for the latter to protect themselves in larger groups.

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