The Alluring Margay

The Margay (Leopardus wiedii) is an arboreal cat, native to Central America. It is well adapted to life in the trees, with a long tail, wide, soft paws, large claws and the ability to rotate its hind paws 180° around its longitudinal axis. This makes it the only cat that can descend from a tree headfirst. The unusual rotational capacity of its hind paws also enable it to hang upside down from branches by its back feet (Oliveira, 1998).

Image: Photographer Lucas Z. Dolowy

During their expedition in the field, a team of researchers interviewed local Amazonian Indians and woodworkers. Multiple reports claimed that the Margay had been witnessed imitating vocalizations of their target prey species, which consists mainly of arboreal mammals.

Image: natureafield.com

The researchers reported the first ever published observation of a margay imitating the Wild Pied Tamarin (Saguinus bicolor). Over a period of almost an hour, they watched as a Margay began imitating calls very similar to that of the Pied Tamarin pups. A male member from the group of tamarins began to investigate, checking the trees for any sign of the mysterious pups. After several minutes, the Margay emerged from its hiding place and quickly approached the group of primates. Emitting a loud screech, the male tamarin alerted the rest of the group and all the tamarins escaped without harm (de Oleviera Calleia et al., 1998).

Although this was an unsuccessful hunt, it demonstrated the ability for the Margay to so accurately imitate the prey’s calls and attract them. This is suggested to be a technique used to reduce energy expenditure. 

It was also mentioned by the Amazonian locals that the prey targeted by the Margay (including the agouti and other arboreal birds and mammals) had sharp calls, similar to those that the felines were able to produce. The Margay is one of a few species of cats that use these imitations of prey to attract and capture them, and shows a special adaptation to life in the jungle of Central America.

References:

Oliveira, T.G, 1998. Leopardus wiedii. Mammalian Species, [Online]. 579, 1-6. Avaliable at: http://www.science.smith.edu/msi/pdf/i0076-3519-579-01-0001.pdf [Accessed 14 March 2014]

de Oliveira Calleia, F., Rohe, F., Gordo, M. 1998. Hunting Strategy of the Margay (Leopardus wiedii) to Attract the Wild Pied Tamarin (Saguinus bicolor). Neotropical Primates [Online]. 16, 32-34. doi: http://dx.doi.org/10.1896/044.016.0107  [Accessed 14 March 2014]

Fishing With Green-backed Herons

The Green-backed Heron is a bird with an extraordinary talent: fishing for its food using bait. Located in areas around the world such as the USA, Africa, and more specifically, Kyushu in Japan, both adult and juvenile birds have been observed using a variety of baits to catch fish in ponds.

Images: Photographer Chris Mazzarella

A Japanese scientist, H. Higuchi, spent approximately 60 hours over the months of June, July and August, observing the herons around a pond in Kyushu, Japan. The types of bait used by the herons included flies, adult insects, insect larvae, earthworms, twigs, leaves, berries and other plant material. Feathers were also seen being used. The Japanese herons were seen using a wide variety of bait, whereas in the United States, birds more specifically used bread, fish pellets, mayflies and feathers. Bait availability was found to be subject to the time of the year.

As shown below, flies were the most successful form of bait used by both adults and juveniles, however, adults had a wider range of success using the different types of bait, whereas the juveniles were successful only with flies. Many attempts were documented of juveniles using twigs and leaves, but to no avail.

Image: Journal Article: Bait-fishing by the Green-backed Heron Ardeola striata in Japan

The heron’s technique of fishing involved collecting the bait when they arrived onsite at their feeding ground, and watching for prey from the side of the pond. The birds would then throw their bait in the water, and crouch down, supposedly to avoid being spotted by their prey. As their prey would approach the bait on the surface, the herons rushed forward to the fish and collected their meal.

Adult herons that chose bait in the form of twigs were seen holding down longer twigs under their feet, and snapping off pieces with their beak to make smaller and more tantalising lures.

There were a few issues with the overall fishing technique, and it was seen mostly in juveniles who were still struggling to perfect it. Two main problems were commonly seen

1.  Juveniles would throw the bait in the water, and forget to crouch down, giving away their ambush position to their prey
2.  When juveniles used twigs, feathers and leaves, they were not broken down into small enough pieces and were not of interest to the fish.

Due to their inexperience, it was not uncommon for the frustrated juveniles to resort to eating their selected insect baits after being repeatedly unsuccessful in their fishing attempts.

Fishing with the use of bait is not the primary method of feeding in Green-backed Herons, as they have been seen simply ambushing fish without the use of any lures of any kind. This adaptation to the use of baits may have evolved behaviorally due to an easier method of finding food, whereby the prey approaches the predator, as opposed to the predator seeking the prey. It is a more energy efficient method, and as stated in Higuchi's (1986) paper, 85.7% of the observed birds were successful using flies as bait.

A video published by Youtube user "TINKERPOPPYIMBA" shows an adult Green-backed Heron fishing (with success!) using a piece of bread.

Reference:

HIGUCHI, H. (1986), Bait-fishing by the Green-backed Heron Ardeola striata in Japan. Ibis, 128: 285–290. doi: 10.1111/j.1474-919X.1986.tb02677.x

Tales of the Thresher Shark

The family of Alopiidae comprise of three Thresher shark species: the Common Thresher (Alopias vulpinus), the Bigeye Thresher (Alopias supercilious), and the Pelagic Thresher (Alopias pelagic us).

As part of a study conducted off Pescador Island in the Philippines, a team of scientists from the School of Ocean Sciences of the Bangor University in Wales sent scuba divers down between the hours of 9am and 6pm to film the hunting strategies of the Pelagic Thresher (Alopias pelagicus). Thresher sharks are easily distinguishable by their long ribbon-like caudal fin, which can be the same length as the shark’s body, and it has been thought that they used their tail to hunt.

Image: Photographer Rafn Ingi Finnsson

Pelagic Thresher sharks reach up to a maximum of around 3.5m, and prey mostly on Indian sardines which are found surrounding Pescador Island. The Thresher shark's unique technique involves swimming at speed directly into a bait ball, where they use an overhead whipping technique, whereby both pectoral fins are drawn together, pushing the front of their body down. The back half is thrown upward and the tail is slapped into the bait ball. A diagram is below to help make this a little easier to picture.

Image: Journal Article: Thresher sharks use tail-slaps as a hunting strategy (cited below)

After careful analysis of the footage that was taken of the sharks during these activities, it was found that the tip of the tail moved so quickly that the frame rates of the cameras used were unable to keep up with the motion, giving only a blurred image of the tail tip. Bubbles were also seen surrounding the tail during this particular moment of movement, suggesting that the velocity was so high that it caused pressure changes in the surrounding water column resulting in gas particles diffusing and forming small air bubbles, which grew in size. This pressure change stuns the fish, giving the shark time to turn around and grab their prey.

The unusual hunting tactics of this species of shark, and the specific prey that it targets suggests that such a high energy demand during the overhead tail whip must require a high return in food. On averages, the studied sharks collected around 3 fish on average after each tail slap; the most successful catching 7 in one go. As stated in the paper, it appears that the Thresher shark’s pectoral and caudal fins were evolved for the purpose of hunting, and using the tail whipping technique.

For those who are wondering what this all looks like put together, here is some video footage from the original study provided by Youtube channel: Animal Wire.

Reference:

Oliver, S. P., Turner, J. R., Gann, K., Silvosa, M., & Jackson, U. (2013). Thresher sharks use tail-slaps as a hunting strategy. PLoS One, 8(7) doi:http://dx.doi.org/10.1371/journal.pone.0067380