Opportunistic Orcas

Killer whales (Orcinus orca) are a species of oceanic dolphin, and are the second most widespread mammal on Earth (Ford, 2009). They are found in both the Pacific and Atlantic Oceans, around Antarctica and much further north into the Arctic. 

Similarly to human populations, genes are partly influenced by culture, and in recent years the effect of ‘cultures’ has become evident in global killer whale communities. Ecologically specialised groups of orcas are known as 'ecotypes', and are found worldwide. Different ecotypes of orcas reside in different areas, hunt differently, and even have different language equivalents (Reisch et. al, 2012).

Image: An orca breaches itself to reach a sea lion pup playing in the shallows. Photographer Frank Wirth (Accessed 25 May, 2014)

There are a variety of orca ecotypes, each specialising in certain types of prey. In studies conducted in the North Pacific over 40 years, no Resident Killer Whale (fish specialists) had ever been recorded taking mammalian prey, and no Transient Killer whale (dolphin, porpoise and seal specialists) had ever been recorded taking fish prey (Herman et. al, 2005). A variety of techniques for hunting are used, and vary from group to group. These can include intentional stranding or beaching, bubble netting, wave washing off ice floes, tail smacking, endurance based exhaustion tactics and drownings.

Image: A group of orcas approach a seal resting on an ice floe. Photographer Göran Ingman (Accessed 25 May, 2014)

Due to complex social bonds within families, it is thought that young members of the pod are  educated through both observation and direct lessons, with a recent study conducted in 2013 showing that orcas can perform action imitation behaviours, where they observe a behaviour from another individual, and copy it (Abramson et. al, 2013).

Such significant differences have lead to a potential divergent speciation of the orcas, with ecotypes of different regions showing a variety of changes in overall size, body coloration and markings (Reisch et. al, 2012). 

Image: Sourced from nmfs.noaa.gov (Accessed 25 May, 2014)

As there are so many different hunting techniques in this species, I have linked only one video.

PLEASE NOTE: For all the pinniped lovers out there, there is no happy ending.

Video with thanks to Discovery on Youtube: 

https://www.youtube.com/watch?v=hPge_0lea3o&feature=kp

References:

Abramson, J.Z., Hern ández-Lloreda, V., Call, J., Colmenares, F. (2013) Experimental evidence for action imitation in killer whales (Orcinus orca). Animal Cognition. 16(1): 11-22

Ford, J.K.B. (2009) ‘Killer Whale – Orcinus orca’ in Perrin, W.F, Würsig, B.G. and Thewissen, J.G.M’s Encyclopedia of Marine Mammals, Academic Press, London. pp. 650 – 657

Herman, D. P., Burrows, D. G., Wade, P. R., Durban, J. W., Matkin, C.O., LeDuc, R. G., Barrett-Lennard, L.G., Krahn, M. M. (2005) ‘Feeding ecology of eastern North Pacific killer whales Orcinus orca from fatty acid, stable isotope and organochlorine analyses of blubber biopsies’ Marine Ecology Progress Series. 302: 275-291. http://www.int-res.com.elibrary.jcu.edu.au/abstracts/meps/v302/p275-291/

Reisch, R., Barrett-Lennard, L. G., Ellis, G. M., Ford, J.K.B, Deecke, V. B. (2012) ‘Cultural traditions and the evolution of reproductive isolation: ecological speciation in killer whales?’ Biological Journal of the Linnean Society, 106: 1–17

Creepy Cookiecutter Sharks

There are two species of Cookiecutter Shark; Isistius brasiliensis and Isistius plutodus. They are found in warm waters surrounding the equator, especially around islands and in deeper waters of up to 1000m. They are make vertical migrations towards to surface at night and it is at this time that they are thought to make contact with most of their prey (Stevens, 2013).

Image: Sourced from noaa.gov [Accessed 16 May 2014]

Image: Sourced from australianmuseum.net.au [Accessed 16 May 2014]

Cookiecutter Sharks are considered ectoparasitic, and feed on a wide variety of large marine animals including sharks, squid, whales, dolphins, seals, pelagic fishes and in more recent reports, deceased and living humans (Gallo-Reynoso & Figueroa-Carranza, 1992). The Cookiecutter Shark gets its name from its characteristic feeding behaviour. Large eyes on this animal show that it is very much a visually oriented predator. The shark uses a combination of muscles in the upper jaw and fleshy lips to suck onto prey, and then cut out a circular plug of flesh using their sharp upper and lower teeth. The result is literally a circular cutout of the prey’s flesh, and is the signature attack remnant of this animal’s feeding technique. Failed attempts result in crescent shaped lesions in the prey (Hoyos-Padilla et. al, 2013).

A recent article by Hoyos-Padilla et. al (2013), described the attack of a Cookiecutter shark on one of the ocean’s leading predators, the Great White Shark (Carcharodon carcharias). The observation was made off the coast of Isla Guadalupe, home to a large population of a variety of seals, which in turn attracts large numbers of Great White Sharks. Waters off this coast can drop to depths of up to 3,600m, with temperatures of 18 - 22°C, it provides an ideal location for the residence of Cookiecutter sharks. Divers involved in a cage diving operation took photos of a subadult male white shark displaying the characteristic bite mark of a Cookiecutter. Directly adjacent to the bite mark, a crescent shaped scar can be seen, suspected as a failed attempt at a bite by the Cookiecutter shark. This attack shows the broad range and the daring attacks made by Cookiecutter sharks. This photo is the first known photographic evidence of an attack on a Great White Shark by Cookiecutters (Hoyos-Padilla et. al, 2013).

Image: Sourced from Hoyos-Padilla et. al (2013) journal article: Observation of an attack by a Cookiecutter Shark (Isistius brasiliensis) on a White shark (Carcharodon charcharias) [Accessed 16 May 2014]

In 2011, the first documented attack on a live human being was reported in Hawai’i. This attack was an unprovoked incident, and involved a 61 year old Caucasian man who was completing a long distance swim across the Alenuihāhā Channel. This distance was a 47.5 km swim, and takes approximately 16-20 hours to complete. A kayak and support boat, complete with first aid and emergency communication, accompanied the swimmer. The attack took place at approximately 8.00pm, and was thought to have been caused by the presence of Purpleback Flying Squid (Sthenoteuthis oualanisnsis). The squid were attracted to the swimmer due to the navigation lights on the support kayak, which was paddling in a 1 meter proximity of the swimmer. Squid were so close to the swimmer that on several occasions the man was bumped by the animals. Purpleback Flying Squid are a known target prey of the Cookiecutter shark, and not long after making contact with the squid, the man felt a sharp pain on his chest. He swam directly to the kayak, and during his attempt to get into the kayak; he felt a second pain in his leg.

Image: Sourced from Honebrink et. al (2011) journal article, First Documented Attack on a Live Human by a Cookiecutter Shark (Squaliformes, Dalatiidae: Isistius sp.) Image (a) shows the failed bite attempt on the chest, image (b) shows the successful bite mark on the calf, 7 days after the incident.

The man survived the attack, but the injury required a skin graft and many weeks of healing. This was not the first reported attacked on a human, however it is the first on a live human. The particular shark responsible was suspected to be Isistius brasiliensis, due to previous sightings in the area. Cookiecutter shark bite marks have been suspected in two incidents that were reported to the International Shark Attack File (ISAF). Both attacks were on deceased humans, the first a man who was found after going missing from a fishing trip, and the second on a suicidal female who was found 6 days after being pronounced missing (Honebrink et. al, 2011).

These incidents were both considered as scavenging events, showing that Cookiecutters are just as likely to scavenge as they are to attacking live prey.

References:

Gallo-Reynoso, J.P., Figueroa-Carranza, A.L. (1992). A Cookiecutter Shark wound on a Guadalupe Fur Seal male. Marine Mammal Science. 8(4): 428 – 430. Doi: 10.1111/j.1748-7692.1992.tb00060.x

Honebrink, R., Buch, R., Galpin, P., Burgess, G.H. (2011). First Documented Attack on a Live Human by a Cookiecutter Shark (Squaliformes, Dalatiidae: Isistius sp.). Pacific Science. 65(3): 365 – 374. doi: 10.2984/65.3.365

Hoyos-Padilla, M., Papastamatiou, Y.P., O’Sullivan, J. Lowe, C.G., (2013) Observation of an attack by a Cookiecutter Shark (Isistius brasiliensis) on a White shark (Carcharodon charcharias). Pacific Science. 67(1): 129 – 134. doi: 10.2984/67.1.10

Stevens, J. (SSG Australia & Oceania Regional Workshop, March 2003) 2003. Isistius brasiliensis. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2.

Glorious Golden Eagles

The Golden Eagle (Aquila chrysaetos) is a notorious and well-known bird of prey found in the Northern Hemisphere. Found in the mountains of North America, Europe and Asia, they have powerful talons and a wingspan of 2.3m, making them the perfect predator to take on a variety of reptilian and mammalian prey. The powerful talons on the eagle allow it to grab hold of and ride larger prey and crush bones and cartilage, until the victim is killed from shock, injury or exhaustion. Its sharp beak is designed for tearing skin and flesh (Macmillan Encyclopaedia  2003).

Golden eagles have been reported to hunt a variety of animals in a variety of ways, and have even been used throughout history as companions to mounted hunters.

Image: Photographer Taipo Kaisla (Flickr.com)

Cases of the eagles dropping items such as rocks or even the prey themselves have been often reported, however, hardly documented correctly. In a recent article, Dr Edward Koch (2012) states that he observed a juvenile Golden Eagle dropping rocks on Dusky Grouse (Dendragapus obscurus) in an attempt to either injure their prey or flush them out of the long grass. There are no known reports to this behavior previous to that seen in south-central Idaho by Dr Koch. In the case of slower moving animals, the eagles use a technique of low flight with a slow descent attack, to ensure accuracy. Animals such as tortoises have been seen being captured and flown up to heights of 10m+, to be dropped onto a rocky surface. This breaks open their tough, protective shell and gives easier access to the eagles for a meal (Watson, 2010). In a video that has gone viral on Youtube, a Golden Eagle can be seen grabbing an unsuspecting goat and throwing it off a cliff face. 

[NOTE: I won't post this video because it was a little on the sad side, and may be a bit much for some viewers.]

Photographer: Jimmy Nelson (beforethey.com)

Golden eagles have also been seen targeting other predators. Used by Khazak hunters in western Mongolia for centuries, tamed female Golden Eagles selected for their superior strength and size, and intent to hunt (supposedly due to strong maternal instincts to provide for their young). 

Falconers still use the Golden Eagles to hunt today, and still use them for traditional means to collect furs of the foxes for their families. The Red Fox (Vulpes vulpes) and Corsac Fox (Vulpes corsac) are the two target species, although in other cultures the eagles are even used to target adult wolves (Soma, 2012). Eagles are carried on the arm of the hunter, who is mounted on a sturdy Mongolian pony. 

Although this may not be a natural hunting technique of the Golden Eagle, it illustrates the diversity in prey choice that these large and beautiful birds are capable of targeting.

Video with thanks to BBC One: https://www.youtube.com/watch?v=-Y3Dl0BGFfw

References:

‘Golden Eagle’ (2003) in The Macmillan Encyclopaedia, Macmillan Publishers Ltd, Basingstoke, United Kingdom.

Accessed: 9 May 2014, from Credo Reference

Koch. E.D. (2012) Juvenile Golden Eagle (Aquila chysaetos) drops rock near Dusky Grouse (Dendragapus obscurus). Journal of Raptor Research. 46(4): 407-407

Soma, T. (2012) Intangible Cultural Heritage of Arts and Knowledge for Coexisting with Golden Eagles: Ethnographic Studies in “Horseback Eagle-Hunting” of Altai-Kazakh Falconers. The International Congress of Humanities and Social Sciences Research p 307 - 316

Watson, J. (2010) The Golden Eagle. 1st ed. London: A & C Black.

Sneaky Sailfish

The Atlantic Sailfish (Istiophorus albcans) is a member of the billfish family, characterized by their elongated and narrow rostrum (bill). Despite being one of the fastest fish in the ocean, recent studies have found that their speed is not the defining factor in a successful hunt, but in fact their bill. Hunting in groups, sailfish herd schools of sardines up towards the surface to feed (Domenici et. al, 2014).

Image: Photographer James Scott Flickr.com

Image: Domenici et. al paper
cited in references

A study published in April 2014, documented the behavior of a sailfish school off the coast of Mexico. Over a week of filming, researchers filmed groups of sailfish up to 40 individuals strong, hunting adult sardines (Sardinella aurita). The sardine school was pushed to the surface by the sailfish, and also targeted above by other predators such as frigate birds (Fregata magnificens) and pelicans (Pelecanus occidentalis). One by one, the sailfish would take turns in chasing the sardine school, pushing their bill into the school, and either individually tapping sardines, or slashing their bill through the entire school. These techniques did not result in the immediate capture of prey, but it was after several damaging attacks on the school that the sailfish were successful in acquiring and ingesting the prey. It was assumed at the time that sailfish only attacked individually, as opposed to as a group, to avoid injury to each other. Previous to this recent study, this technique was only speculated due to stomach contents collected from sailfish that had been caught. Fish in the stomach of the sailfish were sometimes found to have damaging gashes and a significant loss of scales (Domenici et. al, 2014).

Image: Photographer James Scott Flickr.com

As seen in other larger marine vertebrates such as orcas, dolphins and whales, speed and agility can be an issue when prey is significantly smaller than the predator. It is thought that the rostrum on the sailfish (and probably other billfish species) is a morphological adaptation, designed to be narrow as it slices through the water at speeds that are some of the fastest recorded in marine vertebrates ever. The means that the speed of the bill is significantly quicker than the swimming speed of the prey, and it is virtually impossible for the prey, being sardines in this case, to outrun the bill of the sailfish. In no observed instances during the study were sailfish seen to impale or spear sardines (Domenici et. al, 2014). It was also found that the behaviour of the sardines closest to the bill during the attack was the same as those that were out of the bill range, which suggested that the fish had not even noticed the presence of the bill. This may also be another underlying reason as to why the bill is so narrow, because visually it is undetected by prey. 

It is also noticeable in the video (see below!) that the sailfish change colour and raise their dorsal fins as they approach the sardine school. Although not much is known about this behavior, it is possible that the characteristically large dorsal fin is used for herding the school or stability on approach, and their change in colour is potentially linked with excitement, or visual communication with other sailfish in the vicinity (Domenici et. al, 2014). Seeing as this study is only recent and just the beginning of what may be more of an insight into the world of sailfish behavior, it is likely that further research will be undertaken in the future.

Video Credit: Alexander Wilson (youtube.com)

References:

Domenici, P., Wilson, A.D.M, Kurvers, R.H.J.M., Marras, S., Herbert-Read, J.E., Steffensen, J.F., Krause, S., Viblanc, P.E., Couillaud, P., Krause, J. (2014) How sailfish use their bills to capture prey. Proceedings of the Royal Society of Biological Sciences. 281(1784):1471 - 2954. doi: 10.1098/rspb.2014.0444