Grannies of the Sea

­Orcinus orca, photo by S. Blanc on www.arkive.org 

What do humans and whales have in common?

  

        Killer whales (Orcinus orca) and the short-finned pilot whales (Globicephala macrorhynchus) have comparable post-reproductive lifespans. Just like human females, killer whales undergo menopause after they have reached a certain age. They have the longest post-reproductive lifespan of all non-human animals. Female orcas usually stop reproducing during their 30’s to their 40’s but can live until their 90’s, as compared to males that rarely live beyond their 50’s [1].

        Aside from the mortality of the females being higher, their post-reproductive stage renders a higher survival rate to their pod, especially to their male progenies. These so called “grandmothers” may serve as teachers, guides, and keepers of the clans or pods’ traditions [3]. According to a recent study that was conducted for about 35 years, females that had undergone menopausal stage exhibit a strong leadership to its pod. During periods wherein food is scarce, they are most likely to lead the group’s activities, especially when food source such as salmons are low in supply or extremely difficult to locate [2]. The mothers are able to share their long experience in the waters which gives them an advantage in foraging.

        Compared to females, males are more likely to follow their mothers as they conceive the ecological knowledge of their mothers useful. It is known that once their post-reproductively-aged mother dies, the sons have a higher probability of dying compared to the females [2]. From this, it can be said seen that the males highly depend on their mothers for their survival.

        Aside from the killer and pilot whales, there has been no evidence or data in other non-human animals that can suggest similar post-reproductive behavior [1].

            To know more about whales, visit SeaLifeBase.

_______________________________________

[1] Foster, E.A., Franks, D.W., Mazzi, S., Darden, S.K., Balcomb, K.C., Ford, J.K.B., and Croft, D.P. (2012) Adaptive Prolonged Postreproductive Life Span in Killer Whales. Science. 337:1313

[2] Brent, L.J.N., Franks, D.W., Foster, E.A., Balcomb, K.C., Cant, M.A., and Croft, D.P. (2015) Ecological Knowledge, Leadership, and the Evolution of Menopause in Killer Whales. Current Biology. 25: 746-750

[3] Allen, S.G., Mortenson, J., and Webb, S. (2011) Field Guide to Marine Mammals of the Pacific Coast. University of California Press: Berkley, California. 261p.

Written by:

Ocean Giants: Giant Squid

Last week we talked about the Kraken, that it's a squid-like sea monster and that its identity can be either of the two known largest extant squids. First was the heaviest, the colossal squid Mesonychoteuthis hamiltoni (read article here). The second is the longest, the giant squid Architeuthis dux with a cosmopolitan distribution.

Photo taken by Tsunemi Kubodera from Ogasawara Islands, off Tokyo on December 4, 2006 [1].

There are many different species listed under the genus Architeuthis, 21 nominal species in total. But based on a genetic study conducted by Guerra et al (2013), all species are synonyms of A. dux; thus, there is only one giant squid. Furthermore, like the majority of deep sea species, little is known of its biology. Obviously it's a predator; it feeds on fishes and other cephalopods. It has a short life cycle; spawning occurs only once and the females die after bearing their eggs. The largest recorded species measured 12 m in length, unfortunately there was no record of its weight. Studies on its growth and mortality were very limited since getting a sample population from the ocean was tough. Thus, if you have other information on them, which you wish to include in our information system, please e-mail us at sealifebase@fin.ph or join us as a collaborator.

_________________________
[1] Accessed from http://animals.nationalgeographic.com/animals/invertebrates/giant-squid/
[2] McClain CR et al (2015) Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ 2:e715. Accessed from https://peerj.com/articles/715/
[3] Guerra A et al (2013) Architeuthis dux: única especie de calamar gigante en el mundo. MOL. Revista de la Sociedad de Ciencias de Galicia 53:46-53.
[4] Bolstad KS et al (2004) Gut contents of a giant squid Architeuthis dux (Cephalopoda: Oegopsida) from New Zealand waters. New Zealand Journal of Zoology 31(1):15-21.


Written by

Ocean Giants: Colossal Squid

Who here have watched the movie "Clash of the Titans"? Remember the scene when Zeus shouted "Release the Kraken!" to his men? Kraken actually refers to a squid-like sea monster and among the family of squids, there are two known largest species. First is the heaviest - the colossal squid Mesonychoteuthis hamiltoni commonly found in the Antartic.

The short clip above presents the largest specimen ever caught, it weighed 495 kg and measured 4.2 m in length [1]; but the measurements stated are underrated. Experiments conducted by the Te Papa staff from the Museum of New Zealand showed that fresh specimens can shrink up to 22% when preserved and the specimen above was believed to have shrunk by 14%. Unfortunately, only 9 adult specimens have been recorded and were not enough to fully study their biology [2]. Thus, if you have other information on them, which you wish to include in our information system, please e-mail us at sealifebase@fin.ph or join us as a collaborator.

_________________________
[1] McClain CR et al (2015) Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ 2:e715. Accessed from https://peerj.com/articles/715/
[2] The Museum of New Zealand Te Papa Tongarewa. The Squid Files. Accessed from http://squid.tepapa.govt.nz/the-squid-files


Written by

Mother knows best! Don't we all agree?

Harp seals (Pagophilus groenlandicus) are famous for being white and fluffy, which makes them adorable; but did you know that the white harp seals we see are pups? Adults on the other hand are black-faced with silver-gray body [1].

 

(Young harp seal suckling, photo by M. Watson posted www.arkive.org)

Like any other mammal, there is a special bond formed between the mother and her young. In the case of harp seals, the mother “noses” its offspring immediately after its birth not only to recognize its scent but also for her to be able to find her pup after foraging [2, 5]. Foraging takes a few hours a day and the mothers need to eat more during the nursing phase (which lasts about 12 days) to provide milk to their pups [3, 4, 5]. They also use their sense of smell to protect their young by detecting predators on ice [1], and to get back to their pups in case there is a need to relocate them due to the unstable ice floe where they gave birth on. [6]

Newborns are sedentary and weigh around 20 lbs which is almost nothing compared to a well fed adult at around 300 lbs. [2, 6] The pups can gain an average of 5.5 lbs per day, because their mother’s milk contains 25 to 40% fat in comparison to a cow’s milk that only contains 5% fat [2]. As soon as the pup fattens up and the nursing period ends, they are then ready to live on their own. The mothers swim off leaving them on the ice in search of a new mate.

Quite a short time to start becoming independent, huh?

To know more about harp seals, visit SeaLifeBase.

__________________________ 

[1] Lavigne, D.M. (2009) Harp seal Phoca groenlandica. In pp. 542-546, Perrin, W.F., Wursig, B., Thewissen, J.G.M. (2009) Encyclopedia of Marine Mammals, Second Edition. Academic Press: London. 1316pp.

[2]  Dougan, J.L., & Roland, K. (1982). The Ice Lover: Biology of the Harp Seal (Phoca groenlandica). Science, New Series 215(4535):928-933.

[3] Ellis, R. (2003). The Empty Ocean. Island Press, 367p.

[4] Innes, S., Lightfoot, N., & Stewart, R. E. A. (1981). Parturition in Harp Seals. Journal of Mammology 62(4):845-850.

[5] Lydersen, C. & Kovacs, K. M. (1999). Behaviour and energetics of icebreeding,

North Atlantic phocid seals during the lactation period. Marine Ecology Progress Series 187:265–281.

[6] Van Opzeeland, & I.C., Van Parijs, S.M. (2004) Individuality in harp seal, Phoca groenlandica, pup vocalizations. Animal Behaviour 68:1115-1123.

Written by:

World Migratory Bird Day 2015: Energy – make it bird-friendly!

Photo from www.worldmigratorybirdday.org

World Migratory Bird Day was initiated  in 2006 and is an awareness-raising campaign which highlights the conservation of migratory birds and their habitats. This annual event is celebrated every second weekend of May and organized by two international wildlife treaties, the United Nations Environment Programme (UNEP) - the Convention on the Conservation of Migratory Species of Wild Animals (CMS), and the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA).

This year’s celebration has the theme “Energy – make it bird-friendly!”, which aims to emphasize the importance of utilizing energy technologies that do not inadvertedly pose threats to migratory bird species and to their habitats. Empowering actions toward this goal requires proper planning, design and risk assessment. Therefore, this must be participated not only by authorities, organizations, experts and the energy sector but also by an ordinary people of the society.

Search through SeaLifeBase’s collection of about 400 seabirds to know more.

Source:

9-10 May 2015 World Migratory Bird Day. www.worldmigratorybirdday.org [Accessed 05/06/2015].

Written by:

Demise of an ‘indeterminate’ Plesiochelyid turtle from rising sea levels

 Photo reinterpration by Iván Gromicho

A discovery of sea turtle remains from Jaén, Baetic Cordillera adds knowledge on the oldest sea turtles that once existed on Earth millions of years ago. The supposed new species, Hispaniachelys prebetica, turned out to be a misnomer (i.e. deemed invalid) upon reinterpretation of the sole specimen from Jaén. Since evidence is meager, the sea turtle fossil is classified as an ‘inderterminate’ species of Plesiochelyidae, a diverse group of reptiles from the European Jurassic. This means that the specimen possibly fits in one of the previously defined species of the group [1,2].

As experts point out, the Plesiochelyids from 160 million years ago certainly do not resemble sea turtles today. Growing evidence obtained from Spain supports this claim. Unlike that of the agile, migratory, adventurous sea turtles we see today, the first European sea turtles’ anatomy –unfortunately - restricted them to the coastlines. This constraint and the changing sea levels that occurred 145 million years ago obliterated them [1,2]. That’s natural selection, after all.

Currrently, scientists are working to unravel the diversity in Plesiochelyids.

To ponder more on Plesiochelyidea, refer to the link http://www.bioone.org/doi/pdf/10.4202/app.2012.0115. SeaLifeBase also has information for the 7 living species of sea turtles. Happy learning everyone!

____________________

[1] Plataforma SINC (2015, March 23). First European sea turtles became extinct due to changing sea levels. ScienceDaily. Retrieved from http://www.sciencedaily.com/releases/2015/03/150318074232.htm

[2] Pérez-García, A. (2014). Reinterpretation of the Spanish Late Jurassic “Hispaniachelys prebetica” as an indeterminate Plesiochelyid turtle. Acta Paleontologica Polonica 59(4):879-885.

Written by: