Risso’s and Pilot life history, behavior and physiology characteristics

Damon Gannon Mote Marine Lab

William McLellan UNC Wilmington

Risso’s dolphin (Grampus grisues ) grandis = great & pis = fish, gris = gray

1 Field ID Characteristics Total length = 10’ – 12’ Max weight 500 – 600 lbs.

Gray to white coloration Gray back ground color White color from scarring Large prominent Big black eye

Distribution & Abundance

Specific abundance estimates are currently unknown

Best available abundance estimates is the sum of two 1998 surveys that had the most complete coverage of the species =

29,110 (CV=0.29)

NOAA 2005 Stock Assessment Reports (Draft)

2 Risso’s

Source: OBIS-SEAMAP and NOAA

Short-finned pilot whale (Globicephala macrorhynchus ) globi = round cephala = head, macro = large rhynchus = snout

3 Field ID Chacteristics

Total Length= 15’ - 18’ Max Weight= 3,000 – 4,000 lbs

All black

Difuse white anchor between fins

Large bulbous head

Very large dorsal fin

Long-finned pilot whale (Globicephala melas ) globi = round cephala = head, melas = black

4 Field ID characteristics

Total Length= 16’ – 18’ Max Weight = 4,000 0 5,000 lbs

Dark black w/ white cape behind dorsal fin

Very prominent white anchor between fins

Very round head

Very long peduncle

Distribution & Abundance

Specific abundance estimates are currently unknown

Best available abundance estimates is the sum of two 2004 surveys that had the most complete coverage of the species =

30,847 (CV= 0.27)

NOAA 2005 Stock Assessment Reports (Draft)

5 Globicephala spp.

Source: OBIS-SEAMAP and NOAA

Short-Finned Long-Finned

Source: OBIS-SEAMAP

6 Individual Movements

Mate, B. et al. 2005. Movements and dive habits of a satellite-monitored longfinned pilot whale (Globicephala melas ) in the northwest Atlantic. Marine Science 21(1):136-144

Long-finned Short-finned

Fin length does not define species!

Significant overlap of fin length

7 Life History

Reproductive Calving Female Repro Longevity (yr) Maturity (yr) Interval (yr) Gestation (mo) Longevity (yr) M: 46 M: 17 L-Fin F: 59 F: 6-9 5 ~12 40

M: 45 M: 17 S-Fin F: 62 F: 8-9 5-8 ~15 36

M: 13? 13-14 Risso 20-40 F: 3-4 ? ?

Food Habits Long-Finned Pilot Stranded Bycaught (DWF Trawl) n=8 n=30

1 1

4 5 5 Loligo 17

7 Spiny Dog Illex Squid 5 47 Atl. Atl. Mackerel 77 31 Histioteuthis Chiroteuthis

Gannon et al. 1997 Gannon et al. 1997 (Mar. Mamm. Sci.) (Mar. Ecol. Prog. Ser.)

8 Food Habits Short-Finned Pilot Whales Fishes Scopelogadus mizolepis (Big Scale) 43% Merluccius sp. (Silver/offshore ) 1% Unknown fish 6% S. mizolepis

Squids Brachioteuthis riisei (common arm squid) 10% Loligo sp. (Long-finned squid) 10% Histioteuthis reversa (reverse jewell squid) 7% Taonius pavo 5% Chiroteuthis spp. (Long-armed squid) 3% Loligo Abraliopsis 3% Mastigoteuthis sp. 1% Histioteuthis arcturi 1% Lepidoteuthis grimaldii (Grimaldi scaled squid 1% Ommastrephidae (Short-finned squid) 1% Unknown Squid 8% H. reversa

Source: Vanessa Jordan, unpublished data

Food Habits Risso’s Dolphins

Mostly squid

9 Diving

Nowojchik, R. et al. 2003.Movements and dive behavior of two stranded, rehabilitated long-finned pilot whales (Globicephala melas) in the northwest Atlantic. Science 19(1):232-239.

Foraging Behavior: Long-Finned Pilot Whales

• Appear to feed mostly at night • Dive to depths of at least 650 m (~2,100 ft)

References: Gannon 1995, Gannon et al. 1997 (Mar. Ecol. Prog. Ser.), Baird et al. 2002 (Mar. Ecol. Prog. Ser.)

10 Long-finned pilot whales demonstrated to use suction to capture prey

• Captive (rehabilitation at NEA) • Kinematic study from video-records • 1st quantitative study of suction feeding

Werth, A. 2000. Mar. Mam. Sci. 16(2):299-314.

Feeding Mechanics

• Suction feeding (Werth 2000, Mar. Mamm. Sci.)

• Normally Swallow Prey Whole

Pilot whales suck!

11 Echolocation

Comprised of three distinct processes:

• Sound production

• Sound reception

• Signal processing

Sound Production

Bottlenose dolphin

No Vocal Chords

No External ears

How do they produce, and/or receive sounds?

12 Sound Production and Reception

Toothed whales produce high frequency sounds on top of their head at the blowhole and travel through the “”

Copyright © Dolphin Research Center

They receive sound through the lower jaw and is directed to the ears by fat channels that have similar properties of water

CT Scans

Computed tomography (CT) scans provide the opportunity to put the data into an anatomical context

http://www.bio.sdsu.edu/faculty/berta.html

13 Tursiops Echolocation clicks

14 Target Detection

Diameter of target must be > 1 wavelength

_ = c/f

Wavelength (meters) = Speed of sound (m/sec) ÷ Frequency (Hz or Cycles/sec)

S-Fin Pilot Whale: _ = 1530 m/s / 60000 cyc/s = 0.025 m

Risso’s Dolphins: _ = 1530 m/s / 65000 cyc/s = 0.024 m

“Flashlight Beam”

15 Au & Snyder 1980

16 Passive Listening vs. Echolocation

• Costs of Echolocation – Metabolic – Ecological (alerting competitors, predators, prey)

• Passive Listening – Killer whales (Barrett-Lennard et al. 1996) – Bottlenose dolphins (Gannon et al. 2005)

Au & Snyder 1980

17 Passive Listening vs. Echolocation

• Costs of Echolocation – Metabolic – Ecological (alerting competitors, predators, prey)

• Passive Listening – Killer whales (Barrett-Lennard et al. 1996) – Bottlenose dolphins (Gannon et al. 2005)

18 Hearing

Question for PLTRT:

How much of the interaction that has been observed is due to feeding on the catch vs. feeding on the bait?

19