Rigor Vitae: Life Unyielding

Wednesday, March 07, 2007

THE TASTEFUL TRIONYCHIDAE


Utah's paucity of turtles is a subject I've complained about at length, on this blog and elsewhere, but I take solace in knowing that among the three species that barely make it into this state, we can claim the magnificent Spiny Softshell (Apalone spinifera). The three softshells I've seen in southwestern Utah probably descended from New Mexican turtles that were introduced into the Lower Colorado River around 1900. They took well to that famous Arizona air, and dispersed throughout the Gila River drainage, and up the Colorado into Glen Canyon and the Virgin River drainage, and west to the Salton Sea and San Diego county. The native distribution of this species runs from Northwestern Vermont and southern Ontario through most of the eastern U.S., to eastern Colorado, and south to southern Taumalipas. Another introduced population is doing well in the Maurice River system in southern New Jersey. Disjunct populations in the Ottawa River, Lake Champlain, and the upper Missouri in Montana are surely relicts from an earlier, more expansive range. In 1805, Meriwether Lewis remarked at the number of softshells at the confluence of the Missouri and what he named “Turtle Creek,” presently known as Bullwhacker Creek, northwest of Bozeman. In 1960, my pal John Legler found an isolated population of very dark softshells in the Cuatro Ciénegas basin in Coahuila, Mexico, which he and R. G. Webb christened Trionyx = Apalone ater. Since that time, drainage canals were dug into the basin, bringing in outside water and Texas Softshells (A. spinifera emoryi), which hybridized with the A. ater, which is generally no longer considered a distinct species.

The Spiny Softshell is a pretty typical member of the family Trionychidae, which boasts 14 modern genera and some 22 species found in North America, Africa, Asia and the Indo-Australian region. The family has been around since at least the late Jurassic, and was distributed nearly worldwide by the end of the Mesozoic. Only two related, monotypic families, represented today by the Central American River Turtle (Dermatemys mawii) and the Fly River Turtle (Carettochelys insculpta) [above] of New Guinea and Australia, are more adapted to freshwater living than the softshells. The smooth, scuteless shell with flexible rims which gives these reptiles their names affords a profile that is both hydrodynamic and stable. Softshells enjoy burying themselves in sandy river bottoms, and can do so with astonishing speed, shuffling into the substrate with their carapace edges. From this position their long necks allow them to snap at close-passing prey or bring their nozzle-like snouts to the surface for a breath of air. A softshell can stay submerged for very long periods, absorbing enough oxygen through its pharynx, cloaca and skin to maintain a resting metabolic level. A few species enter brackish water, and the Nile Softshell (Trionyx triunguis) [top illustration] has been found in the open sea. Presumably, this African reptile managed to colonize parts of Turkey, Syria, Lebanon and Israel by crossing the Mediterranean. Several Asian species have dispersed across the Indonesian and Philippine archipelagos.

All softshells are primarily carnivorous, but most species also eat some amount of vegetable matter. Females of the three American softshell species (Apalone spp.) are much bigger than the males, and prey mostly on fish, while their mates dine more on crayfish and other invertebrates. When not ambushing prey, the swift and shifty softshells are capable active hunters. Recent observations have shown the Nile Softshell to spend over half of its waking time engaged in play behavior. When not hunting, playing, or laying buried, most softshell species habitually bask on snags and sandbars, pointed toward deep water and ready to lurch into it at the slightest provocation. Fast, intelligent, and hard to hang on to, these turtles are virtually impossible for a human to catch without tools. Once caught, they are well equipped to defend themselves with sharp and powerful claws and beaks. Soon after emerging from hibernation in the spring, mating takes place in the water. A couple of months later, the female hauls up onto land and digs a nest in the sand, usually depositing from four to two dozen eggs, depending on her size. Large Nile Softshells have been recorded laying clutches of over 100. The incubation period varies from species to species; that of the Spiny Softshell is about 60 days.

Modern softshells are placed into two subfamilies. The typical softshells (Trionychinae) comprise 11 genera, Trionyx, Apalone, Dogania, Palea, Pelodiscus, Rafetus, Aspideretes, Nilssonia, Amyda, Pelochelys and Chitra. The three remaining softshell genera contain the flapshell turtles (Cyclanorbinae), remnants of an ancient and poorly-understood group most easily distinguished by plastron flaps that can hide the hind legs. The monotypic Lissemys punctata haunts sluggish waters in Pakistan, India, Sri Lanka, Nepal, Bangladesh and Myanmar. The African Genera Cycloderma and Cyclanorbis contain two species apiece, and are distributed across most of Tropical Africa. Very little is known of these turtles' natural history, particularly the West African Cyclanorbis senegalensis (above).

The Trionychids include the biggest freshwater turtles. An 18-inch female Spiny Softshell looks like a discarded trash-can lid basking on river detritus, but she's far from the largest member of her clan. The Nile Softshell can exceed a yard in shell length, while the Narrow-headed Softshell (Chitra indica) of South Asia has been measured at 44 inches, and the Asian Giant Softshell (Pelochelys bibroni)has been measured at 50 inches.


A particularly big softshell resides in Hoan Kiem Lake, in downtown Hanoi. This lake is remarkable for its place in Vietnamese legend. It is said that after defeating the occupying Chinese army in the 15th century with a divine sword that a farmer had pulled from the water, the emperor Lê Loi was boating on this lake, when Kim Qui, the Golden Turtle God, swam up to him, snatched the sword from his hand, and returned it to the depths. Over the past five centuries, sightings of giant turtles in the lake have been rumored, and in 1967, during the height of the war, the Hanoi Food Company pulled a 400 lb. whopper from the lake. While government and company officials argued about what to do with the reptile, it died, and its mounted remains are on display at the Ngoc Son Temple, on an island in the lake. Around this time, two smaller members of the species were killed, and over the past couple of decades a very large individual with a recognizable white spot on its head has been seen and photographed numerous times (above). In 2000, Hà Dinh Dúc, of Hanoi National University, named the species Rafetus leloii, but this name and two others, Pelochelys hoguomensis (S.A., 1999) and Rafetus hoankiemensis (Devaux, 2001) were rejected by the herpetological community. Professor Dúc maintains that the turtle belongs to a distinct species (he also maintains that it's over 500 years old, and is the very individual that took the sword from Lê Loi), but it is generally agreed that it probably belongs to the species Rafetus swinhoei, an extremely rare Chinese species that was considered extinct until 1988. If so, the known range of the species extends further south than previously thought. Rumors of R. swinhoei in southern Viet Nam have yet to be substantiated, in fact, the species has not been confirmed in the wild since 1972, when one was caught and transferred to the Shanghai Zoo. It is feared that this animal, the one in Hoan Kiem, and three other Chinese captives are the last remnants of the species (one died at the Beijing Zoo in 2005). Unfortunately, most good nesting beaches on Hoan Kiem Lake have been cemented over, and breeding prospects are poor, assuming more than one individual exists there. Eggs from several Hoan Kiem softshell nests have been taken and hatched in the lab, but so far they have all yielded the more common Pelodiscus sinensis. A photograph taken in November 2005 shows the turtle to have sustained a severe shell injury (above right).


If captivity can save R. swinhoei, it won't be the first softshell species to enjoy the experience. The Black Softshell (Aspideretes nigricans) [left] died out in the wild before it was described to science in 1875. The 200 or so surviving individuals live in a man-made pond in Nasirabad, near Chittagong, Bangladesh. These reptiles are said to be descended from sinners turned into turtles by Sultan al-Arefin Hazrat Bayazid Bostami, an 18th century Islamic saint. The large turtle pond is connected to a shrine devoted to Saint Bostami, and the worshippers protect the turtles, which are extremely tame.
_____________________
upper: HIPPOPOTAMUS & NILE SOFTSHELLS (1995) acrylic 20" x 30"
second: FLY RIVER TURTLE (2004) acrylic 18" x 24"
third: SPINY SOFTSHELL TURTLE & TIGER SALAMANDER LARVA (1988) watercolor 16" x 13"
fourth: Photograph of Cyclanorbis senegalensis taken by CPBvK at Village des Tortues, Rufisque, Senegal 2001
fifth: Photographs of Rafetus swinhoei by Hà Dinh Dúc; VietNamNet
lower: Photograph of Aspideretes nigricans ETI World Biodiversity Database

13 Comments:

Blogger burning silo said...

Those are three wonderful turtle paintings, Carel. I especially like the second one.

7:11 AM  
Anonymous Tedd Greenwald said...

Great paintings of wonderful creatures. Here is some good news about Softshell Turtles in FL, yessssssssss.

http://myfwc.com/whatsnew/08/statewide/News_08_X_TurtleClosed.htm

Seems the majority of turtle meat goes to Asia and not to our local families. I would think that someone would farm softshells and I would have no problem with that. Keep the wild turtles where they belong.

www.teddgreenwald.com

9:39 AM  
Anonymous Anonymous said...

My sons just found a 16 1/2 in spiny soft shell yesterday. She is beautiful.

9:44 AM  
Blogger environmentalist7 said...

I saved a soft shell today from the road (it was kicking though!). It almost got ran over several times. I moved it back over to the canal close by. I realized though that I had a little blood on my fingers, so it must have gotten a little injured. I was wondering how well they can sustain injuries?

2:26 PM  
Blogger cpbvk said...

Environmentalist7: I'd say chances are good your turtle's injuries were just minor scrapes from the pavement. Their plastrons are very tender. I wouldn't worry too much about her.

9:50 AM  
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