THE NORTHERN LEOPARD FROG

 

Lithobates pipiens^[1][3][4][5] formerly Rana pipiens,^[6][7] commonly known as the northern leopard frog, is a species of leopard frog from the true frog family, native to parts of Canada and the United States. It is the state amphibian of Minnesota and Vermont. 

 

The northern leopard frog is a fairly large species of frog, reaching about 11 cm (4.3 in) in snout-to-vent length. It varies from green to brown in dorsal color, with large, dark, circular spots on its back, sides, and legs.^[8] Each spot is normally bordered by a lighter ring. A pair of dorsolateral folds starting from the back of the eye runs parallel to each other down the back. These dorsolateral folds are often lighter or occasionally pinkish in colour. Also, a pale stripe runs from the nostril, under the eye and tympanum, terminating at the shoulder. The ventral surface is white or pale green. The iris is golden and toes are webbed.Tadpoles are dark brown or grey, with light blotches on the underside. The tail is pale tan.

Brown morph northern leopard frog in a wood chip pile in Iowa

The northern leopard frog has several different color variations, with the most common two being the green and the brown morphs, with another morph known as the burnsi morph. Individuals with the burnsi 

Near Welland Canal, Ontario

Northern leopard frogs have a wide range of habitats. They are found in permanent ponds, swamps, marshes, and slow-moving streams throughout forest, open, and urban areas.^[11] They normally inhabit water bodies with abundant aquatic vegetation. In the summer, they often abandon ponds and move to grassy areas and lawns. They are well adapted to cold and can be found above 3,000 m (9,800 ft) above mean sea level. Males make a short, snore-like call from water during spring and summer. The northern leopard frog breeds in the spring (March–June). Up to 6500 eggs are laid in water, and tadpoles complete development within the breeding pond. Tadpoles are light brown with black spots, and development takes 70–110 days, depending on conditions. Metamorph frogs are 2–3 cm (0.79–1.18 in) long and resemble the adult.

 

 This species was once quite common through parts of western Canada and the United States until declines started occurring during the 1970s. Although the definitive cause of this decline is unknown, habitat loss and fragmentation, environmental contaminants, introduced fish, drought, and disease have been proposed as mechanisms of decline and are likely preventing species' recovery in many areas.^[8] Many populations of northern leopard frogs have not yet recovered from these declines.

 

 Northern leopard frogs are preyed upon by many different animals, such as snakes, raccoons, other frogs, and even humans. They do not produce distasteful skin secretions and rely on speed to evade predation.

They eat a wide variety of animals, including crickets, flies, worms, and smaller frogs. Using their large mouths, they can even swallow birds and garter snakes. In one case, a bat was recorded as prey of this frog.^[12] This species is similar to the pickerel frog (Lithobates palustris) and the southern leopard frog (Lithobates sphenocephalus).

The northern leopard frog produces specific ribonucleases to its oocytes. Those enzymes are potential drugs for cancer. One such molecule, called ranpirnase (onconase), is in clinical trials as a treatment for pleural mesothelioma and lung tumors. Another, amphinase, has been described as a potential treatment for brain tumors.^[13]

The northern leopard frog has been a preferred species for making discoveries about basic properties of neurons since the 1950s. The neuromuscular junction of the sciatic nerve fibers of the sartorius muscle of this frog has been the source of initial data about the nervous system.^{[14][15][16][17][18][19][20]}

The northern leopard frog is a popular species for in vitro experiments in muscle physiology and biomechanics due to the ease of accessibility for investigators in its native range and the ability of the sartorius muscle to stay alive in vitro for several hours. Furthermore, the reliance of the frog on two major modes of locomotion (jumping and swimming) allows for understanding how muscle properties contribute to organismal performance in each of these modes.

Northern leopard frogs occur from Great Slave Lake and Hudson Bay, Canada, south to Kentucky and New Mexico, USA.^[21][22] It is also found in Panama, where it is endemic to the central cordillera and western Pacific lowlands, although this is most likely an undescribed species.^[1] They occupy grasslands, lakeshores, and marshes. 

 

 

 

 

 

 

 Range of L. pipiens

 

 

 

 

 

 

 

 

THE BLACK- NECKED CRANE

 

The Black-necked Crane (Grus nigricollis) is a medium-sized crane in Asia that breeds on the Tibetan Plateau and remote parts of India and Bhutan. It is 139 cm (55 in) long with a 235 cm (7.8 ft) wingspan, and it weighs 5.5 kg (12 lbs). It is whitish-gray, with a black head, red crown patch, black upper neck and legs, and white patch to the rear of the eye. It has black primaries and secondaries. Both sexes are similar. Some populations are known to make seasonal movements. It is revered in Buddhist traditions and culturally protected across much of its range. A festival in Bhutan celebrates the bird while the Indian union territory of Jammu and Kashmir considers it as the state bird.

 At Bronx Zoo, New York, USA.

 

Description

 

 

This medium-sized crane is mostly grey with a black head and neck. The lores and crown are naked and dull red. A small patch of white feathers are present below and behind the eye. The tail is black and makes it easy to distinguish at a distance from the similar looking common crane which has grey tail.^[2]

 

From Phobjikha Valley, Bhutan.

The black-necked crane summers mainly in the high altitude Tibetan Plateau. The breeding areas are alpine meadows, lakeside and riverine marshes and river valleys. They also make use of barley and wheat fields in these areas. Wintering areas tend to be in sheltered valleys or lower altitudes. The largest populations are in China with smaller numbers extending into Vietnam, Bhutan and India.^[3] Small populations have been noted in northern Sikkim.^[4] A small group of 20 to 40 was once known to regularly visit the Subansiri area in the Apa Tani valley^[5] until 1975^[6] and vagrants have been recorded in Nepal.^[7]

 

 

In 1996 there were about 4,000 of the birds, most of whom spent their winters in Tibet in the valleys of the Nyanga, Lhasa and Pengbo rivers and the middle reaches of the Yarlung Tsangpo.^[8] The Hutoushan Reservoir in the Pengbo valley is an important winter resting place, with a 96 square kilometres (37 sq mi) Linzhou Black-necked Crane Preservation Zone established in 1993.^[9] Black-necked cranes also winter in small numbers in two valleys of western Arunachal Pradesh, India. These are Sangti and Zemithang.^[10][11][12]

 

Behaviour and ecology

 

Black-necked cranes forage on the ground in small groups, often with one bird acting as a sentinel. In winter, the groups arrive and leave the feeding grounds together, but may split into family groups, each group keeping their own small feeding territories in a big marshes or fields.^[6] They spend nearly 75% of the day foraging with peak feeding in the early morning and late afternoon.^[3] While foraging, they keep walking and they also walk long distances between the feeding spots. In this manner, they cover several kilometers a day while foraging.^[13] They feed on the tubers of sedges, plant roots, earthworms, insects and other invertebrates, frogs and other small vertebrates. They may also feed on fallen grains of barley, oats and buckwheat and will sometimes dig up and feed on potatoes, carrots and turnips.^[3][14] Their loud trumpeting calls are similar to those of other cranes.^[2]

 A 1938 photograph of a flock in the Brahmaputra valley

These birds are very wary, but in some areas they are accustomed to the local people who do not disturb them. These cranes appear to be able to distinguish people in traditional dress and are especially wary of others.^[13]

100 odd of this species come to India every year for breeding. Photograph has been taken at Tso Kar, Ladakh, Jammu and Kashmir, India.

 

 

Like many other crane species, they are believed to form long-lasting pair bonds and dancing displays are made during the breeding season. The breeding birds are territorial and will chase away any intruders of the same species immediately, though they are generally tolerant of other species.^[13] The nest site is usually a pre-existing mud island inside a large shallow wetland, sometimes shared along with bar-headed goose. The nest varies from a scantily lined scratch in the ground to a structure made of grass, rushes and weeds with a depression in the centre, sometimes the eggs laid directly on the grass without any structure.^[15][16] Eggs are laid mainly in May and June. One or two eggs.^[2][17] The birds are relatively more wary when the young ones are small. Till the time when the young ones are able to fly, the family kept moving around the nesting location, but later the family started traveling far and wide in the course of a day. Though the young ones are able to forage independently, usually they accompany the parents during foraging. Short, subdued nasal "kurrr" calls are used by the family to keep in contact and also by adults to indicate availability of food to juveniles. The adults were found to feed the young ones mainly with fish in Ladakh, adults fishing like herons.^[13] They are endangered because of the hunters.

 

A couple of black-necked Tibetan cranes spotted in 2013 near Yamdrok Lake, Tibet Autonomous Region

 

 

 

The estimated population of the black-necked crane is between 8800 and 11000 individuals. These birds are legally protected in China, India and Bhutan. However habitat modification, drying of lakes and agriculture are threats to the populations. In many areas, dogs belonging to herders are a major threat to young birds. An incident of leopards preying on the roosting cranes during the night has been recorded from the Phobjika valley of Bhutan.^[18] In Bhutan, collisions with power lines have been another cause of mortality in some areas.^[1][19] Eggs may also be preyed on by ravens that may use the opportunity 

 

 

provided when humans disturb the parents.^[3] The drying of wetlands can cause increased accessibility of the nests leading to predation while a rise in the water level can submerge nests.^[20] Loss and degradation of habitat are the main threats facing the black-necked cranes. The problems are most serious in the wintering areas, where wetlands are extensively affected by human activity including irrigation, dam construction, draining, and grazing pressure. In Tibet, widespread changes in traditional agricultural practices have reduced the availability of waste barley and spring wheat.^[20]

Populations in Bhutan are well protected both culturally and legally although some disturbance from tourism exists.^[21]

The black-necked crane is evaluated as Near Threatened on the IUCN Red List of Threatened Species.^[1] It is listed on Appendix I of CITES.

See also