Odontocetes found in the Southern California Bight

Transcription

1 Odontocetes found in the Southern California Bight Aimée Lang Marine Mammal and Turtle Division Southwest Fisheries Science Center 18 October 2016 San Diego Natural History Museum Whalers

2 Outline: What is an odontocete? Review of most commonly seen odontocetes in waters off San Diego Identification Behavior Fun facts Quick overview of less often seen species Photo: RH Defran

3 What is an odontocete? Mysticetes (14 species) Cetaceans (89 species) Odontocetes (75 species) Use baleen to filter feed Generally larger Not known to utilize echolocation Two blowholes Use teeth to capture food Typically small to medium sized Utilize echolocation to locate prey Single blowhole

4 Odontocetes: Very diverse group! All photos from WDC website

5 San Diego County Top Six Short-Beaked Common Dolphins (Delphinus delphis) Long-Beaked Common Dolphins (Delphinus capensis) Bottlenose Dolphin Coastal (Tursiops truncatus) Bottlenose Dolphin Offshore (Tursiops truncatus) Risso s Dolphins (Grampus griseus) White-Sided Dolphins (Lagenorhyncus obliquidens)

6 Common Dolphin Short-beaked: Delphinus delphis Long-beaked: Delphinus capensis Slender body Long distinct beak Photo: WDC High dorsal fin Bright coloration with crisscrossing hourglass pattern Color patterns less distinct in young and juvenile dolphins Photo: T. Stenton, WDC Both D. delphinus

7 Common Dolphins: Behavior Schools can be in the thousands; often found in association with other species Gregarious and energetic, often surface-active Diet varies with region Commonly bow-ride (boats and large whales!) High bycatch numbers D. capensis Photo M. Sidwell, WDC

8 Differences: Morphology Long-beaked: D. capensis Photo: K. Debler, WDC Larger (<2.2m), sleeker Longer beak with flatter melon More muted coloration Short-beaked: D. delphis Smaller (< m), more robust Shorter beak with more rounded melon Photo: N. Hodgins, WDC

9 Differences: Behavior and ecology Short-beaked: D. delphis More abundant: ~ ,000 Prefer deeper cooler offshore waters Long-beaked: D. capensis Less abundant: 25,000 43,000 Prefer shallower, warmer waters closer to the coast and on shelf

10 Common Dolphin: Take Home Tri-colored Distinct rostrum D. capensis Common mistakes: Pacific White-sided dolphin With each other D. delphis

11 Bottlenose dolphin: Tursiops truncatus 2.5 to 3.0 meters Falcate dorsal fin Short robust rostrum Gray color with lighter belly Bow-riders/surface active

12 Bottlenose dolphins (Tursiops truncatus) off San Diego Coastal stock Abundance: Small population (~400) Distribution: Typically forage in waters <1km from coast (10-30m deep) Behavior: Cautious but curious around boats Offshore stock Abundance: Large population (>1000) Distribution: Typically found >=4 km from shore, often associated with islands Behavior: Readily associate with other species and boats Morphological and genetic differences exist between the two stocks

13 Tursiops truncatus: Coastal stock: Studied since the early 1980s using photo-identification

14 Population size small but stable over last couple of decades Individuals show little fidelity to any given area, but instead roam throughout a coastal corridor that extends at least as far south as Ensenada, Baja Mexico Individuals can travel at least as fast as 95km/day Extended range further north in response to warm water events 88 % 94 % Santa Barbara Santa Monica Bay Orange County San Diego Ensenada 88 %

15 93 % Bodega Bay San Francisco Bay Following the 1982/1983 El Nino, PCBDs extended their range north to Monterey Bay Range extension continues; now seen as far north as Bodega Bay May be recolonizing their historic range 72 % 88 % 94 % Monterey Bay Santa Barbara Santa Monica Bay Orange County San Diego Ensenada 88 % 3% San Quintin

16 Since 2005, 44 known porpicides in CA waters Three observed encounters involving 23 individual dolphins, majority known or thought to be adult males Fun (??) facts: Porpicide by coastal bottlenose dolphins Cotter et al Wilkin et al. 2012

17 Risso s Dolphin: Grampus griseus Fifth largest delphinid 3.6 to 4 m long Weight kgs Tall falcate dorsal fin (one of tallest relative to to body size) Large head with bulbous melon Indistinctive beak

18 Photos, Calves born gray to brown, then darken as juveniles As adults, color lighten with age, becoming light gray to white Heavily scarred due to intraspecific interactions (toothrakes) griseus means grizzled, mottled with gray

19 Risso s Dolphin Distribution Map courtesy of the Convention on Migratory Species Distributed worldwide in temperate to tropical oceans Prefer steep shelf-edge habitats m deep CA/OR/WA population estimated at ~12,000 (in 2011)

20 Risso s dolphin: Behavior: Group sizes typically between dolphins, but may form widespread large aggregations in 100s 1000s Often found with other species (offshore bottlenose dolphins, northern right whale dolphins) Feed almost entirely on squid (night and day) Typically have no teeth in upper jaw and only a few teeth in the lower jaw

21 Risso s dolphin: Behavior Slow moving, but can be surface-active Typically not interested in vessels Known to harass gray whales and other species

22 Risso s Dolphin: Take Home Scarred and light colored Tall dorsal Indistinct rostrum Common mistakes: Killer whales (juveniles and adult females) Photo: O.Yates, WDC

23 Pacific White-Sided dolphin: Lagenorhyncus obliquidens

24 Pacific White-Sided Dolphin ( Lags ) Medium sized ~ meters, ~150 kgs Distinct hourglass pattern on flank Large falcate frosted dorsal fin Short rostrum/beak Often in smaller groups (10-20) when feeding, but can form large schools up to 3000+

25 Pacific White-Sided Dolphin Distribution Map courtesy of the Convention on Migratory Species Found in cold temperate waters Typically found in waters from continental shelf to pelagic waters, have been seen to enter deep water inshore passes Usually most abundant in shelf waters off southern California during winter-spring (Nov-April)

26 Pacific White-Sided Dolphin ~30,000 animals in CA/OR/WA Surface active/bow riders Can make rooster tail splash patterns (similar to Dall s porpoise) Readily associates with other species Diet of lantern fishes, anchovies, hake and squid

27 Pacific White-Sided Dolphin: Take home Tri-colored No distinct rostrum Photos, Common mistakes: Common dolphin (more prominent beak, different coloration) Occasionally Dall s porpoise (more triangular dorsal fin)

28 Reminder find Bernardo s picture Photo by Bernardo Alps CLaWS Survey, August 2015

29 Less Common Dolphins off San Diego County

30 Northern Right Whale Dolphin: Lissodelphis borealis ( Lisso s ) Dark slender body with no dorsal fin Pelagic cold-temperate species Often associate with Lags Typically found in large groups From a distance, can be confused with porpoising sea lions!

31 Short-finned Pilot Whales: Globicephala macrorhynchus Relatively common in southern California prior to the El Nino Following the EN, sightings of pilot whales decreased while sightings of Risso s dolphins increased Suggested that Risso s dolphins may have filled niche and taken over Several sightings off Southern California since June 2014, presumably related to the warm water blob

32 Dall s porpoise: Phocoenoides dalli Largest porpoise species (up to 2.4m, 200kg) Striking black and white coloration pattern Triangular dorsal fin ( frosted ) with broad base

33 Dall s porpoise: Phocoenoides dalli Typically small groups (2-12 individuals) Fast swimmers with characteristic rooster tail splash Avid bowriders (unlike other Phocoena sp.) Generally in cool temperate waters; mostly oceanic but can come close to shore in areas with deep water near coast

34 Killer Whale: Orcinus orca Both the transient (Bigg s) ecotype (mammal eaters) and the offshore ecotype (eat sharks, sea lions, fish?) have been recorded in southern California A few sightings of what where thought to be ETP killer whales were made recently (an effect of the blob?)

35 LA Pod: Included individuals ~70 sightings between , most in southern CA Most famous for one female that was known to take a great white shark Last seen in La Jolla in December 1997; possibly shifted range further south?

36 Questions?

37 Dolphin or Porpoise? Dolphin Family Delphinidae Wider range of body lengths, typically more slender bodies Hector s dolphin (1.7m) to Killer whale (~6m) Prominent rostrum Taller, falcate dorsal fin Conical teeth 25+ species Porpoise Family Phoceonidae Generally smaller, stout bodies ~2m or less Short, round rostrum Smaller, triangular dorsal fin with a rounded tip Fused neck vertebrae Flattened, spade shaped teeth 6 species

38 Males v. Females

39 Population Health: Contaminants High levels of DDT documented in 1980s (Hansen 1990) Contaminant analysis of biopsy samples collected from both offshore and coastal bottlenose is ongoing (D. Weller) Are contaminant levels higher in the coastal versus offshore population?

40 Population Health: Skin lesions Santa Monica Bay (Bearzi et al. 2009): 73.4% of coastal dolphins 87.8% of offshore dolphins More prevalent in Monterey Bay: 90% of coastal individuals Cause is unknown Similar to findings in other populations Could be sign of disease and/or related to anthropogenic factors like contaminants

41 Harbor porpoise Unusual Mortality Event in central CA Wilkin et al. 2012

42 Rake marks, lesions, and type of trauma consistent with porpicide by bottlenose dolphins Seasonal occurrence at time of greatest range overlap All June to November Most August to September (Cotter et al. 2012, Wilkin et al. 2012)

43 Porpicide Cotter et al Wilkin et al Since 2005, 44 known porpicides in CA waters Three observed encounters involving 23 individuals All adults 61% known males, + 31% suspected males 16 individuals involved in 2 encounters, 3 individuals involved in all three

44 Porpicide Possible explanations: Aberrant behavior? Too many individuals involved Competition for food? Different ecological niches High levels of testosterone? All attacks occurred during what is considered the breeding season Practice for infanticide? Documented in other populations (US east coast, Scotland) Can increase reproductive success of males But no known cases of infanticide in ENP

45 Bodega Bay San Francisco Bay Monterey Bay 2012 in Bodega Bay 15 sightings, Ensenada,San Diego, Santa Monica Bay, Santa Barbara, Monterey Bay and Bodega Bay, CA Santa Barbara Santa Monica Bay San Diego Ensenada 1984 in San Diego Smooch 28 Years 1000 km