Gray Whales in the North Pacific: History, biology, and current research
Aimée Lang
Marine Mammal and Turtle Division
Southwest Fisheries Science Center
13 October 2015 Photo courtesy of San Diego Natural History Museum Whalers W. Perryman Photo credit: Wayne Perryman, SWFSC Overview:
• Taxonomic history
• Physical description
• Gray whale biology and life history
• How we study gray whales and what we’ve learned! Taxonomic history:
• First described based on subfossil remains from the coast of Sweden (Lilljeborg 1861)
• “Eschrichtius” – named after a Danish zoologist (Dr. Daniel Eschricht) who was the first to suggest the remains might be from a new genus and family
• “robustus” – Latin for strong Relationship to other baleen whales:
• Fossil record is generally sparse but suggests higher diversity in the past
• Today the gray whale is the only living species in its genus and family
• Although traditionally considered morphologically distinct from the rorqual whales, molecular analyses indicate that gray whales are closely related to balaenopterid whales
Sasaki et al. 2005, mitogenome analysis Physical characteristics:
• Heart-shaped blow • Mottled gray and white coloration • Dorsal hump followed by series of 6 to 12 “knuckles” • Yellowish white baleen • Fewest baleen plates of any mysticete (130-180 plates on each side of mouth) • 2-5 throat grooves
Size: • Adult body 11 to 15 m and weigh 45,000 kg • Females are larger than males • Calves 4.6 to 4.9 m at birth and weigh 700-900 kg
Gray whale barnacles (Cryptolepas rhachianecti):
• Considered “obligate commensals” – Attach to whales as larvae – Filter-feeders – Rely on whale’s movements through water to find plankton • A single whale typically carries 100s of lbs of barnacles • Generally thought to be host- specific – But have been found on captive belugas and bottlenose dolphins in San Diego Bay – One record of this barnacle on a stranded killer whale
“Whale lice” • Crustaceans of the family Cyamidae
• Not host-specific (found on other whale species, especially those that tend to inhabit shallower water)
• Three species found on gray whales
• Parasitic - eat skin and dead tissue
• Found on healthy whales but may be much more abundant on whales in poor health Gray Whale Feeding and Diet:
• Gray whales often feed in the mud on the seafloor
“Benthic feeding” Gray Whale Feeding and Diet:
• In the Arctic, the primary prey are benthic amphipods
~ 3 cm long! Gray Whale Feeding and Diet:
• But gray whales are flexible foragers: – They feed both in benthos and in water column – They eat a variety of species, including benthic and mobile amphipods, cumaceans, mysids, crab larvae and herring eggs
Mysid Cumacean Gray Whale Reproduction:
• Sexual maturity between 6 to 12 years of age • Mean date of conception mid- December • Gestation period 13 months • Mean calving date mid-January • Healthy females can reproduce at intervals of two years • Calves weaned at 6-8 months (about mid-August in the Arctic feeding area) Gray Whale Migration • Migrate annually 15,000 - 20,000 km round trip • Takes about 2 months each way • Southward migration begins mid-November and is segregated by age, sex and reproductive condition: – (a) Pregnant females about to have their calves – (b) Non-pregnant females and mature males – (c) immature whales of both sexes • Northward migration begins about mid-February and occurs in two phases: – Phase I = (a) adult males and females without calves, (b) immature whales – Phase II = mothers with calves
Gray Whale Distribution:
• Gray whales went extinct in North Atlantic in 1700s
• Currently gray whales are found only in the North Pacific, where two populations are recognized
• Eastern population
• Western population Distribution of the Eastern population:
• Most of the eastern gray whales feed during summer and fall in ~19,000 animals
Arctic ~200 animals • A small number of whales show “Pacific Coast fidelity to southern feeding Feeding Group” ground between Northern CA and southeastern AK • Overwinter in the lagoons and coastal waters of Baja Mexico during winter/spring • This is where most of the calves are born Status of the Eastern population:
• Commercial whaling on the eastern
population was prohibited in the 1940s 30000 • The population currently contains 25000 ~19,000 animals 20000 • In 1994 the eastern population was 15000 removed from the List of Endangered Abundance 10000 and Threatened Wildlife as it was no 5000 longer considered endangered or
0 threatened under the ESA. 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 Year
Durban et al. (accepted) Status of the Western population:
• Most of what is known is derived from long-term studies of whales feeding off Sakhalin Island, Russia ~19,000 Sakhalin Island, animals • The western population was Russia ~200 probably always smaller than the animals eastern population
• But commercial whaling on the western population continued through at least the 1960s ??? • At one point, some scientists thought that the western population was extinct
• We now know it exists but in small numbers (~150 animals today)
• The western population was listed as Critically Endangered in 2000 by the International Union for the Conservation of Nature Gray Whale Threats • Entanglements in fishing gear • Environmental degradation, exposure to contaminants • Noise (e.g. seismic surveys) related to offshore oil and gas • Ship strikes and associated disturbance • Arctic environmental changes – warming water and loss of sea ice? How do we study gray whales? 1. Counts 2. Satellite tags 3. Photographs 4. Genetic sampling Counts to monitor calf production (northbound migration)
Piedras Blancas, CA Calf production:
Wayne Perryman Southwest Fisheries Science Center
• Conducted from the Piedras Blancas Light House station since 1994 (21st anniversary this past year!) • Counts of northbound whales • Mothers with calves pass very close to shore and after adult and juvenile phase Unofficial 2015 estimate Calf production: ~1420 calves
Estimates of Northbound Calves 1800 1600
1400
1200 1000 800
Calf Estimate Calf 600 400 200 0 1990 1995 2000 2005 2010 2015 Survey Year Correlation with sea ice in Arctic: LOTS OF ICE IN SPRING MEANS FEWER CALVES THE FOLLOWING YEAR!
2.5 Ice Cover 2 Calf Est 1.5
1
0.5
0 1990 1995 2000 2005 2010 2015 2020 -0.5
-1
-1.5
-2 Mechanism: Ice extent in spring of previous year
Ice Extent Ice Low Extent High
High # of calves the following spring! Low # of calves the following spring! But….. The pattern may be changing????
2.5 Ice Cover 2 Calf Est 1.5 LowLow # of# of calves calves the the followingfollowing spring! spring! 1
0.5
0 1990 1995 2000 2005 2010 2015 2020 -0.5
-1
-1.5
-2 In the spring of 2012, the sea ice extent was the greatest it had been during our time series. However, the number of calves that were counted going past PB was relatively high. Learning about predation on gray whales using satellite tags (on killer whales!):
John Durban Southwest Fisheries Science Center Predation on gray whales by killer whales:
Subadult male Bigg’s killer whale attacking a juvenile gray whale; Most of the predation is on calves with some small juveniles taken Satellite tag on a killer whale: Killer whale tracks:
• Estimated ~150 transient killer whales are waiting on gray whale mothers and calves as they cross into the Bering Sea on northward migration • May return to finish carcass later • Most killer whales remain at entrance to Bering Sea but some follow the mother-calf pairs further north • Can be a significant impact on calf production Photo-Identification and Biopsy Sampling off Sakhalin Island, Russia
ID 055 Photo-identification of gray whales: What have we learned about the gray whales off Sakhalin from photos?
• Small population size (~150 animals) • Most animals return year after year, including some animals first identified as calves • Very few reproductive females
Dave Weller • Relatively slow rate of population increase SWFSC • Relatively low calf survival
Biopsy sampling:
Photo collected under SWFSC Permit #14097 What have we learned from genetics?
• There are genetic differences between gray whales that feed off Sakhalin and eastern gray whales • Many of the whales that feed off Sakhalin learn to use the feeding ground from their mothers • First hint that some whales that feed off Sakhalin travel to the coast of North America during winter Distribution:
~19,000 animals
~200 animals
~150 animals
N=2 Two animals sampled off Sakhalin Island were genetically identical to two animals that were sampled while migrating north in ??? the Santa Barbara Channel in 1995 Satellite tagging studies (Mate et al. 2015)
SI
OdL
Varvara: 22,511 km roundtrip!!! Flex: 10 Dec 2010 – 05 Feb 2011 Varvara SE Varvara SE: 24 Nov 2011 – 02 Feb 2012 Varvara NW Varvara NW: 2 Feb 2012 – 14 May2012 Calving area CSL Agent: 25 Nov 2011 – 31 Dec 2011 Distribution:
~19,000 animals
~200 animals
~150 animals N=6
We now know that at least 22 of the ~150 N=2 gray whales off Sakhalin have traveled to the N=14 west coast of North America! ??? But some gray whales remain in the western Pacific year-round: • 22 records of gray whales Pacific coast of Japan - January 2007 off Japan since 1990 – At least two of these records were photographs of whales that were first identified as calves off of Sakhalin Pacific coast of China - November 2011 • 2 records of gray whales off China since 1996
Conservation implications:
• Some whales (“true” western gray whales) do remain in the western North Pacific year-round
• But this number may be very small
• We need to know more about where gray whales are during winter and spring in the western North Pacific (e.g. Japan, China) What’s next? A large whale survey (CLaWS) is currently being Collaborative Large Whale Survey: conducted between northern CA and Kodiak 9 July – 9 November, 2015 Island, AK Dave Weller, Chief Scientist Objectives: 1) Collect photo-id data and genetic samples from the Pacific Coast Feeding Groupof gray whales, especially in areas where we have little information 2) Search for right whales in the Gulf of Alaska 3) Collect photo-id data and biopsy samples from other species of large whales (e.g., fin whales, sperm whales, blue whales, etc.)
Highlights so far…..
All photos collected under SWFSC permit #14097 Thank you! Extra slides
Understanding population structure in a changing environment
• Many marine mammals depend on the Arctic marine ecosystem • The Arctic marine ecosystem is rapidly changing, including: • Dramatic loss of sea ice • Rising sea temperatures • Ocean acidification • These changes will not affect all areas in the same way • Understanding the population structure is critical to evaluate potential impacts of these changes
Jeffries et al. 2013 Case Study #1: Gray whales – a ‘sentinel species’ for monitoring Arctic environmental changes? • Calving rates positively correlated with early-season ice- free conditions
• Shift in distribution on Bering Sea feeding grounds and in timing of southbound migration
• Recordings of gray whales in the Arctic during winter months . Photo courtesy of W. Perryman • Movements of gray whales into the Atlantic Counts to estimate abundance (southward migration)
Wayne Perryman Southwest Fisheries Science Center • Count whales from shore at Granite Canyon late December to mid-February
• Migration is about 2-3 km offshore along the central California coastline
• Counts have been conducted since 1968 Counts to estimate abundance: • Use binoculars and eyes to find groups • Count number of whales in each group Abundance: Mortality Event 1999-2000
Angliss, R.P. and Allen, B.M. 2007 Abundance:
19,126
40+ years of data on the abundance of ENP gray whales!! Shift in migratory timing:
• Approx one week shift in migratory timing since 1980s – Thought triggered by photo-period – But suggests environmental factors – May be related to oceanographic regime shift in late 1970s – may have changed distribution of prey and thus of whales – Could relate to increased population, meaning that whales have to disperse more to find food. – ~6 km/hour southward migration rate. Graphic shows where gray whale tracks intersect with shipping lanes in Southern California. Credit: Lauren Saez, NOAA SWFSC. From Whalewatcher…
• Estimated that 100+ transient killer whales are waiting for gray whales each spring as they cross into Bering Sea • Take mostly calves and some small juveniles; must be able to separate calf from mother • Prize the lips and tongues; usually eat only part of carcass then allow it to sink and come back to it later • Typically try to drown the gray whale • Gray whales typically try to retreat to shallow water to avoid drowning; killer whales do not follow because need to be able to attack from underneath • Estimated that take ~100 calves and 20 juveniles a year; can be significant part of calf production, which is usually 1-8% of population. Estimate 5-50% of production lost due to killer whale predation • Some leave after gray whales pass into Bering Sea, but others follow the whales further north
Assessment of Body Condition
Wayne Perryman Southwest Fisheries Science Center
• The relationship between environmental conditions in the Arctic, especially the spatial and temporal distribution of sea ice, and gray whale physical condition is poorly understood.
• Photographs of southbound gray whales taken from aerial platforms can allow for an assessment of body condition post-feeding. Does This Picture Make Me Look Fat?
Southbound Southbound Pregnant
Condition Index Data From Flights 1996-1998 max width / length So far…
• Aerial photogrammetric sampling of southbound gray whales from 1997-2003, 2013 • Reproductive condition in gray whales can be detected from measurements of length and width in vertical aerial photographs • Northbound adults and juveniles were found to be significantly thinner relative to their length than southbound whales (about 45 - 50 days interval) • Next question: Can vertical aerial photographs be used as a primary data source for tracking population level changes in gray whale condition? Piedras Blancas Light House Station: Piltun Field Camp Most days….. But on the good days… Potential threats:
• Entanglement in fishing gear
– Between 2005 and 2007, four female gray whales entrapped and killed in set nets off Japan • Disturbance from offshore oil and gas activities
– Rapidly expanding oil and gas industry off Sakhalin
Western North Pacific gray whales:
• The population of gray whales in the WNP was probably never as large as that in the ENP • Commercial whaling for WNP gray whales continued through at least 1966 • At least some scientists believed that WNP gray whales were extinct in the 1970s, but their continued existence was later confirmed by sightings and catch records • Little was known about the current status of WNP gray whales until 1995 Anthropogenic Threats:
•19% of whales off Sakhalin show signs of entanglement in fishing gear • 2% show signs of surviving at least one vessel collision
Bradford et al. Killer whale predation:
• 44% of whales demonstrate evidence of attacks by killer whales (Weller et al. 2008) Body Condition: “Skinny whales”
Bradford et al. Distribution:
~19,000 animals
~200 animals
~130 animals ? N=6
N=1 N=2
• 14 records of gray whales off Japan since 1990 N=14 • Most records concentrated between Mar – May • One animal linked to Sakhalin (Weller et al. 2008) ??? • 2 records of gray whales off China since 1996 Arctic sea ice extent for September 16, 2012 was 3.41m sq km. The orange line shows the 1979 to 2000 median extent for that day. The black cross indicates the geographic North Pole. Photograph: National Snow and Ice Data Center
In Sept 2012, Arctic sea ice shrank 18% compared to previous low record (2007) Photo-identification of gray whales: Fossil Record:
Tsai and Boessinger 2015 Fossil Record:
Tsai and Boessinger 2015 Taxonomic history:
• First described based on subfossil remains from the coast of Sweden (Lilljeborg 1861)
• Named after a Danish zoologist (Dr. Daniel Eschricht) who was the first to suggest the remains might be from a new genus and family
• Formally described as distinct by John Edward Gray, head of the Zoology Department at the British Museum of Natural History
• Gray named the genus “Eschrichtius” in honor of Dr. Eschricht
• Some confusion over whether the common name derives from the coloration or from the man who first formally recognized the genus as distinct