Jul 26

Male mountain nyalas (Tragelaphus buxtoni)

Species: Mountain nyala (Tragelaphus buxtoni)

Status: Endangered (EN)

Interesting Fact: The male mountain nyala is larger than the female, and has long, spiralling horns, which may grow to 118 centimetres long. As the male matures, the tips of its horns develop an ivory colouration.

More information: The mountain nyala is an elegant and rather attractively marked antelope and is endemic to the highlands of Ethiopia, where it is found to the southeast of the Rift Valley. Most active in the evening and early morning, the mountain nyala browses on bushes, trees and herbs, and will also take grasses, ferns, aquatic plants and lichens. Individuals often shelter in dense cover such as woodland and heather during periods of extreme cold or heat, and the attractive markings may help to conceal individuals from predators by breaking up its outline.

The mountain nyala population has undergone a substantial decline in recent decades, and has decreased from an estimated 7,000 to 8,000 individuals in the 1960s to perhaps fewer than 4,000 today. The range of the mountain nyala has been reduced dramatically, and the remaining populations have become fragmented, which has made them particularly vulnerable to population declines. The main threats to the mountain nyala come from the negative effects of human activities throughout its range, with increasing human and livestock populations putting ever-increasing pressure on this species through illegal hunting, competition with cattle and predation by domestic dogs, as well as habitat clearance for agriculture, grazing, firewood harvesting, and settlement. Despite being fully protected by law, enforcement of legislation is generally absent, and the mountain nyala is only effectively protected within a small area in the north of Bale Mountains National Park. The mountain nyala is a flagship species for conservation in Bale Mountains National Park, but its future survival will depend on increased protection from illegal activities, and action to reduce or manage human utilisation of the park.

See images and videos of the mountain nyala on Arkive.

Find out more about the wildlife of Ethiopia on Arkive.

Read about the Saint Louis Zoo’s project to conserve the mountain nyala.

Ben Hogan, Wildscreen ARKive PIPS Intern

Jun 7

Atlantic bluefin tuna (Thunnus thynnus)

Species: Atlantic bluefin tuna (Thunnus thynnus)

Status: Endangered (EN)

Interesting Fact: The Atlantic bluefin tuna can swim at speeds of up to 72 kilometres per hour when pursuing its prey.

More information: The enormous Atlantic bluefin tuna can grow to lengths of 4.6 metres and weigh up to 684 kilograms. This fish species has two types of muscle, one for continuous long-distance swimming and the other for short, fast bursts of speed. This amazing adaptation means that individuals of this species are able to swim across the Atlantic Ocean in just 60 days. Although the Atlantic bluefin tuna is generally found swimming in mixed species schools close to the surface of the water, it is capable of diving to depths of up to 1,000 metres when chasing prey. Another fascinating adaptation of the Thunnus genus is the blood exchange system known as the rete mirable which enables individuals to swim in water that is much to cold for other fish. The Atlantic bluefin tuna is a highly migratory species and has a naturally occurring magnetic mineral located in its head that helps with navigation to and from its spawning grounds.

The severe exploitation of the Atlantic bluefin tuna has led to the drastic decline of every known population, particularly in the North Atlantic Ocean. Despite quotas being in place to ensure sustainable numbers are removed from the population, the limits are frequently not respected and unless the legal levels are suitably enforced, it is predicted that some Atlantic bluefin tuna stocks will collapse. The western Atlantic stock may have already collapsed and is now in grave danger of extinction due to overfishing. In the Mediterranean, tuna ranching poses the greatest threat to this species. Individuals are captured alive and taken to a ranch where they are fattened before being sold. Since 1998, catch limits have been in place and in 2006 the International Commission for the Conservation of Atlantic Tunas (ICCAT) established a 15 year recovery plan for the Atlantic bluefin tuna. The plan includes stricter catch limits and closing certain fisheries at specific times of the year to allow the local stocks to recover.

Find out more about Atlantic tuna conservation: International Commission for the Conservation of Atlantic Tunas (ICCAT).

See images and videos of the Atlantic bluefin tuna on ARKive.

Hannah Mulvany, ARKive Content and Outreach Officer.

May 31

Lemur leaf frog (Hylomantis lemur)

Species: Lemur leaf frog (Hylomantis lemur)

Status: Critically Endangered (CR)

Interesting Fact: The lemur leaf frog has the remarkable ability to change colour depending on whether it is active or resting.

More information: The lemur leaf frog is a tiny, highly threatened amphibian from Central America. This species is primarily nocturnal, and spends the day well hidden on leaves. During the day, this frog is a vibrant leaf-green colour, changing to red-brown when it is active. At night, the lemur leaf frog walks stealthily among low vegetation in search of its invertebrate prey. This species breeds during the rainy season, and the female lays between 15 and 30 eggs on leaves that hang over water. After the eggs have hatched, the larvae are washed into the watercourse during heavy rain. This Critically Endangered amphibian is currently found in Costa Rica and Panama, and marginally in Colombia. In Costa Rica this frog is only known from three sites.

The lemur leaf frog has undergone a drastic population decline, estimated to be more than 80 percent loss over a 10 year period. While pigments in the skin of the lemur leaf frog are thought to grant it some resistance, the decline of this species is thought to be due to chytridiomycosis, a disease that is responsible for global amphibian population crashes.  This frog is also threatened by deforestation, especially in Costa Rica.

In Panama, this species is known to exist within at least six protected areas, whereas the habitats of the Costa Rican populations remain unprotected. A captive breeding programme began in 2001 at the Atlanta Botanical Garden, which has been highly successful and has since transferred individuals to other zoos to continue the effort. Other breeding programmes exist at the El Valle Amphibian Conservation Center in Panama, and the Manchester Museum in the United Kingdom.

Find out more about the lemur leaf frog and other species of South America

See images of the lemur leaf frog on ARKive

Find out more about amphibian conservation

Ben Hogan, Wildscreen ARKive PIPS Intern

May 24

Russian sturgeon (Acipenser gueldenstaedtii)

Species: Russian sturgeon (Acipenser gueldenstaedtii)

Status: Critically Endangered (CR)

Interesting Fact: The Russian sturgeon can reach lengths of nearly two and a half metres.

More information: The Russian sturgeon belongs to an ancient and unique group of fish, relics from the time of the dinosaurs. This prehistoric giant was formerly found in the Black, Azov, and Caspian Seas in Eastern Europe and the Middle East, as well as the deep sections of fast-flowing rivers, such as the Volga, Danube, and Ural Rivers. Populations of this species are now mostly found in the lower reaches of these river systems and along coastlines.

The male Russian sturgeon does not reproduce until it is between 8 and 13 years old and only do so every 2 or 3 years, while the female does not reach sexual maturity until it is 10 to 16 years old and then only reproduces every 4 to 6 years. There are two distinct forms of this fish species, the anadromous type which migrates up rivers from the sea to spawn and the freshwater form which remains in its freshwater habitat to spawn, although this form is now thought to be extinct. For the anadromous type, there are two separate migrations, one in spring when spawning occurs in the lower levels of the river and one in autumn when individuals migrate into freshwater where they spend the winter before spawning upstream the following spring.

Vast areas of the Russian sturgeon’s spawning grounds have been lost due to damming and exploitation. Dam construction is highly detrimental to this and other migratory fish species, as the usual migration routes to its spawning grounds are blocked, meaning that individuals either do not reproduce, or spawn in unsafe areas. Pollution in the Caspian and Black Sea basins is causing hormonal imbalances in this species and subsequently a greater number of hermaphroditic, infertile individuals are found in these areas.

The Russian sturgeon was once very important commercially, and its caviar was one of the most sought after of any species. Illegal fishing still continues, despite legal catch quotas being in place, with the illegal catch thought to far surpass the legally set limits. The Russian sturgeon is unprotected in many areas throughout its range and the absence of a strict monitoring system makes the control of fishing very difficult. Despite restocking efforts, the creation of artificial spawning grounds, and the introduction of fish lifts to help individuals to get around dams, the population is still in decline and over the last 15 years, global catches have dropped by 98 percent. As a slowly maturing species, it does not have the ability to recover from overexploitation, especially without complete cessation of fishing.

Celebrate World Fish Migration Day and find out more about why we need to protect these species and their habitats.

Find out more about sturgeon conservation.

See images of the Russian sturgeon on ARKive.

Hannah Mulvany, ARKive Content and Outreach Officer

May 17
Scalloped hammerhead

Scalloped hammerhead

Species: Scalloped hammerhead (Sphyrna lewini)

Status: Endangered (EN)

Interesting Fact: The hammer-shaped head of the scalloped hammerhead is thought to be a mechanism to spread out the ampullae of Lorenzini which are sensory organs that detect electric currents, chemicals and temperature changes.

More information: The scalloped hammerhead can be distinguished from other hammerhead shark species by the ‘scalloped’ front edge of its head. This species has a relatively slim body and is counter-shaded, with a brown-grey or bronze upperside and a white underside. This relatively large shark can grow up to lengths of 4.3 metres and can weigh up to 152 kilograms. Fish, cephalopods, lobsters, shrimp, crabs, other sharks and rays make up the diet of this species, and prey items are usually eaten whole. Generally occurring in the warm temperate and tropical waters of the Atlantic, Indian and Pacific Oceans over continental shelves, the scalloped hammerhead is also known to enter closed bays and estuaries and generally swims between depths of 0 and 275 metres.

Occasionally caught as bycatch by longline fisheries, the scalloped hammerhead is also caught commercially. Various products are made from the body parts of sharks, including shark fin soup from the fins and vitamins from the liver, as well as the meat which is sold for human consumption. Certain parts of this shark’s range are protected, including the area around Melpelo in Colombia, and there are plans to extend the legal protection to other areas. There are no other known conservation measures currently in place for this Endangered species.

Find out more about marine conservation at the Save Our Seas Foundation and Project AWARE.

Find out more about shark conservation at Bite Back and the Shark Trust.

See images and videos of the scalloped hammerhead on ARKive.

Hannah Mulvany, ARKive Content and Outreach Officer

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