Wildebeest

         

          A distinctive, high-shouldered antelope, with a long, broad muzzle and cow-like horns, the blue wildebeest is famous for forming vast migratory herds. The Male weighs up to 290 kg and Female weighs up to 260 kg. The species gets its common name from the silvery-blue sheen to the coat, the base colour of which varies from greyish to brown. The forequarters bear vertical black stripes - the ‘brindled’ colouration that gives the species one of its alternative names - and the front of the face, the long tail, and the mane are also black. The long beard may be black or white, depending on the subspecies. Both the male and female have unridged horns, which curve downward laterally before pointing upward and inward, and in older animals may have a knobby base.

           Five subspecies of blue wildebeest are recognised: the western white-bearded wildebeest, the eastern white-bearded wildebeest, the Johnston’s or Nyassa wildebeest, Cookson’s wildebeest, and the blue wildebeest. the western white-bearded wildebeest, the smallest of these, with the shortest horns, is the subspecies which forms the famous large herds of the Serengeti - Masai Mara. The blue wildebeest can be distinguished from the black wildebeest (or white-tailed gnu).

Range: The blue wildebeest has a wide distribution from Kenya and Tanzania southwards, to Zambia, Namibia, Botswana, Mozambique, northern South Africa and southern Angola, and has been introduced to the Eastern Highlands of Zimbabwe and to farms in Namibia. Cookson’s wildebeest has probably the most restricted range, being found only in the Luangwa Valley in Zambia.

Habitat: Generally inhabiting open short-grass plains, as well as Acacia savannah, open bush land and woodland in drier areas, the blue wildebeest prefers habitats which are neither too dry nor too wet.

Status: Listed as Least Concern (LC) in IUCN Redlist.

Biology: The blue wildebeest is a grazer, its broad mouth adapted to bulk feeding on short grass. However, its dependence on short grass, together with its need to drink at least every other day, limits the species to moist grassland and to areas within reach of water, although interestingly it is also known to survive in waterless regions of the Kalahari by feeding on melons and water-storing roots and tubers. The need to follow seasonal grazing and water supplies leads the blue wildebeest to form some of the largest migratory herds of all antelopes, with those in the Serengeti-Masai Mara ecosystem of Kenya and Tanzania forming part of the world’s largest remaining aggregations of large land mammals. However, not all wildebeest migrate, with some remaining in the same area year-round, generally forming small herds of up to ten females plus immature offspring. The females in these herds tend to establish dominance hierarchies and harass any outsiders who attempt to join. In contrast, the only stable associations in migratory herds are between a female and offspring.

          The blue wildebeest has an unusually restricted breeding season. Around 80 to 90 % of calves are born within a two to three week period, usually at the start of the rains, when conditions are most favourable. This also helps to protect the calves by creating a glut for predators. The female blue wildebeest gives birth annually, to a single calf, after a gestation period of around eight months. The calf follows the female from the moment it can stand, usually within 15 minutes of birth, and is weaned by nine months. The young male is pushed out of the herd by territorial males after the first year, after which it joins a bachelor herd, which may also contain older and non-territorial males. After reaching sexual maturity at three to four years old, the male becomes solitary and attempts to establish its own territory, which may be temporary in migratory populations, or may be continuously occupied and defended for years. Territorial competition between males typically involves ritualised displays, pushing with the horns, and the loud ‘ge-nu’ call that gives the wildebeest its other name, the gnu. The lifespan of the blue wildebeest is around 20 years in the wild.

Migration: Wildebeest are famous for their annual long-distance migration, seemingly timed to coincide with the annual pattern of rainfall and grass growth. The timing of their migration in both the rainy and dry seasons can vary considerably (by months) from year to year. At the end of the rainy season (May or June in East Africa), wildebeest migrate to dry season areas in response to a lack of surface (drinking) water.   When the rainy season begins again, animals quickly move back to their wet season ranges. Every year the animal moves around 3000 kilometer like  clock work. 

          Factors that are suspected to affect migration include food abundance, surface water availability, predators and phosphorus content in grasses. Phosphorus is a crucial element for all life forms, particularly for lactating female bovids. As a result, during the rainy season wildebeest select grazing areas that contain particularly high phosphorus levels. One study found that in addition to phosphorus, wildebeest select ranges containing grass with relatively high nitrogen content. Wildebeest migration at the large-scale is quite likely a consequence of decisions being made by individuals at multiple spatial scales, involving a balance of food abundance, food quality, local density of other wildebeest, social interactions, surface water, perceived predation risk, and culturally (or possibly genetically) learned routes and ranges.

         

          Numerous documentaries feature wildebeest crossing rivers, many being eaten by crocodiles or drowning in the attempt. While having the appearance of frenzy, recent research has shown that a herd of wildebeest possesses what is known as “swarm intelligence”, whereby the animals systematically explore and overcome the obstacle as one. Major predators that feed on wildebeest include the lion, hyena, cheetah, leopard, and crocodile, which seem to favour the wildebeest. Wildebeest however are very strong and can inflict considerable injury to even a lion. Wildebeest have an apparent maximum running speed of around 64 km/hr. The primary defensive tactic is herding, where the young animals are protected by the older larger ones while the herd runs as a group. Typically the predators attempt to cut out a young or ill animal and attack without having to worry about the herd. Wildebeest have developed additional sophisticated cooperative behaviours, such as animals taking turns sleeping while others stand guard against a night attack by invading predators. Scientists are unsure how much is learned behaviourally and how much is hard wired into the DNA of the animal. Wildebeest migrations are closely followed by vultures, as wildebeest carcasses are an important source of food for these scavengers. The vultures consume about 70 % of the wildebeest carcasses available. Decreases in the number of migrating wildebeest have also had a negative effect on the vultures. In the Serengeti Ecosystem, Tanzania, wildebeest may help also facilitate the migration of other smaller-bodied grazers, such as Thomson's Gazelles which eat the new growth shoots on grasses that were stimulated by wildebeest foraging.

          Zebras and wildebeest group together in open savannah environments when there is a high chance of predation. This grouping strategy reduces predation risk because larger groups decrease each individual’s chance of being hunted, and also because predators are more easily seen in open areas. Wildebeest can also listen in on the alarm calls of other species, and by doing so can reduce their risk of predation. 

          One study showed that along with other ungulates, wildebeests responded more strongly to the baboon alarm calls compared to the baboon contest calls even though both types of calls had similar patterns, amplitudes, and durations. The alarm calls were a response of the baboons to lions, and the contest calls were recorded when there was a dispute between two males.

Threat: Although the blue wildebeest is thought to undergo natural periodic population declines due to environmental factors such as drought, the species is also under threat from the spread of human settlement, livestock and agriculture, as well as poaching for meat. If the number of blue wildebeest killed by humans increases as human populations increase, the species could face a permanent decline. However, perhaps the greatest threats are human activities that prevent the blue wildebeest migrating or accessing its seasonal ranges. These include fences, and the elimination of water sources as a result of deforestation and irrigation practices. The dependence of some migratory populations on seasonal access to unprotected areas, where the wildebeest are more vulnerable to poaching and habitat loss, could also result in smaller, resident populations that are confined within protected areas.

Conservation: The blue wildebeest is still widespread and numerous, and occurs in many protected areas throughout its range, including the Serengeti National Park in Tanzania, a World Heritage Site. However, some populations and subspecies are of concern, particularly Connochaetes taurinus albojubatus, which is thought to have undergone large declines. In addition, even within many protected areas the blue wildebeest is already dependent on deliberate management and conservation policies for its survival.

          The Serengeti-Masai Mara ecosystem may contain around 70 % of the global population of blue wildebeest, meaning the future of the population here will have a significant impact on the species overall conservation status. As the dominant large herbivore in many of these areas, wildebeest have a major influence on the whole ecosystem. Monitoring and protection of this distinctive antelope may therefore be essential for the conservation of these ecosystems as a whole.

References:

            http://www.iucnredlist.org/apps/redlist/details/5228/0

            http://en.wikipedia.org/wiki/Wildebeest

            http://animals.nationalgeographic.com/animals/mammals/wildebeest/

            http://www.awf.org/content/wildlife/detail/wildebeest

The Monarch Butterfly

One of the best-known butterfly species, the beautiful monarch butterfly is renowned for its spectacular, long-distance annual migrations. The adult monarch butterfly is brightly coloured, with orange upper wings, interlaced with black veins and surrounded by a wide, black border marked with numerous white spots. While the striking colouration of the upper wings serves as a visual warning to predators that this species is poisonous, the under surface of the wings is duller orange, and helps to camouflage this species against tree bark and other substrates when at rest. Male and female monarch butterflies can be readily distinguished by the fact that the adult male is slightly larger than the female and has a black spot on each hind wing.

Like the adult, the fully-grown monarch butterfly caterpillar is also highly distinctive, possessing bold, yellow, black and white bands over the entire five centimetre-long bodies, with a pair of long black filaments near the head and a pair of shorter filaments towards the rear. During metamorphosis the caterpillar forms a lime-green chrysalis, marked with gold spots and a black, horizontal band edged with gold.

Range: The monarch butterfly has an expansive range extending throughout much of the New World, from southern Canada, south through the entire United States to Central and South America. The two best-known populations are the North American western and eastern migratory populations, which travel vast distances between British Colombia and California, and from Southern Canada, through the eastern United States to central Mexico.

Status: The exact number of individuals insects is not known and yet to be assessed by the IUCN. But it is noticed that about one third of the population is reduced at their usual hibernation ground.

Habitat: The monarch butterfly can be found in a variety of temperate and tropical open habitats. As both the adult and larval stages rely on milkweed for food, the monarch butterfly is typically found at sites, such as fields, meadows, weedy areas, marshes, and roadsides, where these plants are common. During the winter, migratory populations hibernate in fir, pine, oak and cedar forests.

Biology: Although all monarch butterfly populations share the same basic biology, it is the migratory populations, in particular the eastern North American population, which display the most spectacular behaviour. The eastern population migration commences at the summer breeding grounds, which range as far north as southern Canada. During the summer several successive, short-lived generations of monarch butterfly are produced, which complete the entire lifecycle from hatching through metamorphosis to reproduction and death within a period of two to five weeks. The final summer generation, however, has a much longer lifespan, and commences a mass, southward migration in the autumn from the breeding grounds to the wintering grounds, covering distances as far as 4,800 kilometres at speeds of up to 130 kilometres per day. These butterflies, which originate from a breeding range spanning over 100 million hectares, concentrate in forests, in areas which cover less than 20 hectares. 

        Here they form some of the largest single species aggregations known, numbering millions of individuals, which blanket the trees on which they roost. The butterflies remain in a state of relative inactivity for most of the winter, occasionally taking moisture and flower nectar on warm days, but as spring approaches, many commence mating, before returning to the northern breeding grounds. The females lay eggs during the journey, and while most of the winter generation die before reaching the original breeding grounds, once subsequent new generations have become adults, they continue to head north, thereby re-colonising the entire North American breeding range. This two-way, north-south yearly migration is unique amongst butterflies and moths.

Female monarch butterflies lay eggs, usually singly, on a variety of milkweed species, sticking them to the underside of the leaves. After four days, the caterpillar hatches, and eats almost constantly increase in mass by almost 2,000 times over a 9 to 14 day period, before undergoing metamorphosis. This rapid growth is accompanied by five moults, known as “instars”, in which the caterpillar sheds its smaller skin. The caterpillar then forms a chrysalis in which metamorphosis take place over a period of 9 to 15 days. Once emerged, the adult monarch butterfly remains reliant on milkweeds, feeding on nectar from the flowers, although it may also take nectar from a variety of other flowering species. 

Both the caterpillar and the adult are poisonous to most vertebrates due to the accumulation of toxic chemicals produced by the milkweeds. These are accumulated by the caterpillar during feeding, and remain present in the adult’s tissues throughout its life. When attacked, by naïve birds for example, the toxin causes severe vomiting, and ensures that the predator avoids the monarch butterfly in the future. Despite this powerful defence mechanism, monarch butterfly caterpillars are preyed upon by some invertebrates, such as wasps and ants, which are less affected by the toxins.

Threat: Although the monarch butterfly is not considered to be globally threatened, the North American migration is recognised by the IUCN to be an endangered biological phenomenon. This is mainly due to the variety of threats faced by the butterflies at the winter sites, including logging and clearance for agriculture in Mexico, and coastal land development in California. In addition, outside the wintering sites monarch butterflies are further affected by the use of pesticides, habitat loss, the loss of milkweed populations and parasites.

Conservation: In order to protect migratory populations of the monarch butterfly at the wintering grounds in Mexico, in 1986, the Monarch Butterfly Biosphere Reserve was established. This World Heritage property includes more than half of the overwintering colonies of the monarch butterfly’s eastern population.

In 2008, the Commission for Environmental Cooperation created The North American Monarch Conservation Plan, which details a strategy for conserving and maintaining the Monarch butterfly population through international cooperation between Canada, The United States and Mexico. 

The plan’s aims include the decrease or elimination of deforestation at the wintering grounds; addressing habitat loss and fragmentation along the migratory route and at the breeding grounds; public education about the threats faced by this species; and increased monitoring during migrations. Their work will help to ensure that this spectacular butterfly is preserved and that its extraordinary migratory journey will be witnessed by future generations.                                                                                                   

Reference:

http://en.wikipedia.org/wiki/Monarch_(butterfly)

http://www.monarch-butterfly.com/

http://animals.nationalgeographic.com/animals/bugs/monarch-butterfly/

http://www.monarchwatch.org/

The Pygmy Seahorse

           

        The pygmy seahorse is one of the smallest seahorses of the world measuring just 2 cm in height and is undoubtedly one of the most well camouflaged species in the oceans, being extremely difficult to spot among the gorgonian coral it inhabits. So effective is this camouflage that the species wasn’t actually discovered until its host gorgonian was being examined in a lab. Large, bulbous tubercles cover this species’ body and match the colour and shape of the polyps of its host species of gorgonian coral, while its body matches the gorgonian stem. Two colour morphs exist: pale grey or purple individuals scattered with pink or red tubercles are found on the similarly coloured gorgonian coral Muricella plectana, and yellow individuals with orange tubercles are found on gorgonian coral Muricella paraplectana. It is not known whether individuals can change colour if they change hosts, although the ability to change colour according to their surroundings does exist in some other seahorse species.

Range: The pygmy seahorse is known from coral reefs in the tropical western Pacific around Australia (Queensland), Indonesia, Japan, New Caledonia, Papua New Guinea and the Philippines.

Status: The pygmy seahorse is classified as Data Deficient (DD) on the IUCN Red List, and listed on Appendix II of CITES.

Biology: Only known to occur on gorgonian corals of the genus Muricella, the pygmy seahorse is typically found between 16 and 40 metres depth. Adults are usually found in pairs or clusters of pairs, with up to 28 pygmy seahorses recorded on a single gorgonian, and may be monogamous (Each male will have only one female). Unusually, it is the male, and not the female, that becomes pregnant in seahorses. Pygmy seahorses are unique from larger seahorses in other ways. There is no pouch at the base of the tail. The male still incubated the eggs, but he does this in a brooding cavity in the trunk (body) region with a downward facing opening. This is likely an adaptation due to their small size.

Breeding occurs year-round, and gestation averages two weeks, during which the male carries the eggs concealed within his trunk region. In one birth witnessed underwater a male ‘gave birth’ to a brood of 34 live young. The young look like miniature adult seahorses, are independent from birth, and receive no further parental care.

Threat: Very little is known about the total number of pygmy seahorses, population trends, distribution, or major threats. It has therefore been classified as Data Deficient on the IUCN Red List. Because of the unusual and attractive colouration of this small seahorse it is possible that it could be being collected for the aquaria trade, although no international trade in the species has been recorded.

Conservation: All seahorses are listed on Appendix II of CITES, effective as of May 2004, limiting and regulating their international trade. Australian populations of pygmy seahorses are listed under the Australian Wildlife Protection Act, so that export permits are now required, although they are only granted for approved management plans or captive-bred animals. With such limited data available on this fascinating animal, there is an urgent need for further research to be conducted on its biology, ecology, habitat, abundance and distribution, before its status can be properly assessed and conservation measures implemented accordingly. The remarkably effective camouflage of this astonishing species may make such surveys particularly challenging, but hopefully it will also help protect it from exploitation, keeping it safe and hidden in the Pacific reefs where it belongs.

Reference:

http://en.wikipedia.org/wiki/Pygmy_seahorse

http://www.arkive.org/pygmy-seahorse/hippocampus-bargibanti/

http://news.nationalgeographic.com/news/2009/02/photogalleries/new-seahorse-sea-life-found/

http://pygmyseahorses.com/http://www.environmentalgraffiti.com/news-pygmy-seahorse-expert-camouflage-artist