THE PLANS ZEBRA

The plains zebra (Equus quagga, formerly Equus burchellii), also known as the common zebra or Burchell's zebra, is the most common and geographically widespread species of zebra.^[2] It ranges from the south of Ethiopia through East Africa to as far south as Botswana and eastern South Africa. The plains zebra remains common in game reserves, but is threatened by human activities such as hunting for its meat and hide, as well as competition with livestock and encroachment by farming on much of its habitat.
Subspecies include the extinct quagga and six recognized extant subspecies, though there is great variation in coat patterns between individuals. The striping pattern is unique among ungulates in the region, and its functions are disputed. Suggested functions include crypsis, forms of motion camouflage, social signaling and recognition, and discouraging biting flies.
The plains zebra's range is fragmented, but spans much of southern and eastern Africa south of the Sahara. Its habitat is generally but not exclusively treeless grasslands and savanna woodlands, both tropical and temperate. They generally avoid desert, dense rainforest and permanent wetlands, and rarely stray more than 30 kilometers from a water source.
The plains zebra is a highly social species, forming harems with a single stallion, several mares and their recent offspring; there are also bachelor groups. Groups may come together to form herds. The animals keep watch for predators rather than attempting to hide; they bark or snort when they see a predator, and the harem stallion attacks predators such as dogs, hyenas and leopards to defend his harem. The species population is stable and not endangered, though some populations such as in Tanzania have declined sharply.

 

 

Taxonomy

There is a dispute among biologists as to how to properly classify the various species of zebra. It is thought that the plains zebra and mountain zebra belong to the subgenus Hippotigris and that Grévy's zebra is the sole species of subgenus Dolichohippus. This is on account of Grévy's zebra resembling an ass (subgenus Asinus), while the plains zebra and mountain zebra are more horse-like. All three animals belong to the genus Equus along with other living equids. However, recent phylogenetic evidence suggests that the mountain zebras and Grévy's zebras should be classified with asses and donkeys in a lineage separate from the plains zebra.^[3] In areas where plains zebras are sympatric with Grévy's zebras, it is not unusual to find them in the same herds^[4] and fertile hybrids occur.^[5] In captivity, plains zebras have been crossed with mountain zebras. The hybrid foals lacked a dewlap and resembled the plains zebra apart from their larger ears and their hindquarters pattern.

Subspecies

Quagga (E. q. quagga)

Burchell's zebra (E. q. burchellii) in Etosha National Park, Namibia

Maneless zebras (E. q. borensis) are the northernmost and generally the darkest form of the plains zebra

In 2004, C. P. Groves and C. H. Bell investigated the taxonomy of the zebra genus, Equus, subgenus Hippotigris. They published their research in the journal Mammalian Biology. They revised the subspecies of the plains zebra Equus quagga. Six subspecies are now recognizable.^[1]

• Quagga, †Equus quagga quagga – Boddaert, 1785
• Burchell's zebra, Equus quagga burchellii – Gray, 1824
• Grant's zebra, Equus quagga boehmi – Matschie, 1892
• Maneless zebra Equus quagga borensis – Lönnberg, 1921
• Chapman's zebra, Equus quagga chapmani – Layard, 1865
• Crawshay's zebra, Equus quagga crawshayi – De Winton, 1896

Sometimes another subspecies is distinguished in Eastern Zimbabwe and Western Mozambique:

• Selous' zebra, Equus quagga selousi - Pocock 1897

The quagga was originally classified as a separate species, Equus quagga, in 1778. Over the next 50 years or so, many other zebras were described by naturalists and explorers. Because of the great variation in coat patterns (no two zebras are alike), taxonomists were left with a great number of described "species", and no easy way to tell which of these were true species, which were subspecies, and which were simply natural variants. The quagga was the first extinct creature to have its DNA studied. Recent genetic research at the Smithsonian Institution has demonstrated that the quagga was in fact not a separate species at all, but diverged from the plains zebra, between 120,000 and 290,000 years ago, and suggests that it should be named Equus burchellii quagga. However, according to the rules of biological nomenclature, where there are two or more alternative names for a single species, the name first used takes priority. As the quagga was described about 30 years earlier than the Burchell's zebra, it appears that the correct terms are E. quagga quagga for the quagga and E. quagga burchellii for the plains zebra, unless "Equus burchellii" is officially declared to be a nomen conservandum.
Burchell's zebra was thought to have been hunted to extinction. However, Groves and Bell concluded in their 2004 publication that "the extinct true Burchell's zebra" is a phantom. Careful study of the original zebra populations in Zululand and Swaziland, and of skins harvested on game farms in Zululand and Natal, has revealed that a certain small proportion shows similarity to what now is regarded as typical "burchellii". The type localities of the subspecies Equus quagga burchellii and Equus quagga antiquorum (the Damara zebra) are so close to each other that the two are in fact one, and that therefore the older of the two names should take precedence over the younger. They therefore say that the correct name for the southernmost subspecies must be burchellii not antiquorum. The subspecies Equus quagga burchellii still exists in KwaZulu-Natal and in Etosha.

Physical description

Foal displaying brown and white pattern

The plains zebra is mid-sized, smaller on average than the other two zebra species, and thick bodied with relatively short legs. There is some variation in size, based on the animals' condition and subspecies. Adults of both sexes can stand from 1.1 to 1.45 m (3.6 to 4.8 ft) high at the withers (shoulder), are 2.17 to 2.46 m (7.1 to 8.1 ft) long, not counting a 47 to 56 cm (19 to 22 in) tail, and weigh 175 to 385 kg (386 to 849 lb). Males may weigh 10% more than females.^[6][7]
Like all zebras, they are boldly striped in black and white, and no two individuals look exactly alike. They also have black or dark muzzles. The natal coat of a foal is brown and white. All have vertical stripes on the forepart of the body, which tend towards the horizontal on the hindquarters. The northern populations have narrower and more defined striping;^[8][9] southern populations have varied but lesser amounts of striping on the underparts, the legs and the hindquarters.^[8] Southern populations also have brown "shadow" stripes between the black and white coloring.^[8][9] These are absent or poorly expressed in northern zebras.^[8][9]
Embryological evidence has shown that the zebra's background color is dark and the white is an addition.^[10] The first subspecies to be described, the now-extinct quagga, had plain brown hindquarters. There have been various mutations of the zebra's pelage, from mostly white to mostly black.^[11] Rare albino zebras have been recorded in the forests of Mount Kenya.^[12]

Function of the stripes

Variation in coat pattern in Burchell's zebra (E. q. burchellii)

The striping pattern of the zebra is unique among sympatric ungulates. One suggested function for the stripes is to provide crypsis for the animal in tall grass or in the dappled shade beneath bushes and trees.^[13] However, cryptically colored species, such as the kudu and bushbuck, tend to be quiet and stealthy. They freeze when there is danger and flee only at the last moment. By contrast, the zebra is active and noisy,^[13] and makes no attempt to hide itself.^[10] Another suggestion is motion camouflage, that the stripes affect a predator's judgement of the zebra's size, distance and what direction it is going in.^[13] A 2014 study supports this hypothesis, finding that, when moving, the stripes may confuse observers, such as mammalian predators and biting insects, via two visual illusions, the wagon wheel effect, where the perceived motion is inverted, and the barber pole illusion, where the perceived motion is in a wrong direction.^[14] A related hypothesis is that the stripes make it difficult for a predator to single out and learn about an individual during a chase.^[13]
Perhaps the best explanation for the stripes is that they serve a social function.^[10] Individual zebras can apparently recognize each other by their striping patterns.^[15] The stripes may also serve as visual cues for grooming.^[10] In addition, they could serve to help zebra groups stay together when they are fleeing.^[13] A 2012 study suggests that stripes may have developed to discourage biting flies. Experiments have demonstrated that the stripes polarize light in such a way that it discourages tabanids (biting flies) in a manner not shown with other coat patterns.^[16] Another study from 2015 determined that environment temperature is a strong predictor for zebra striping patterns and proposed that the stripes may be related to thermoregulation.^[17]

Ecology

Range and habitat

Plains zebra are highly dependent on water

The plains zebra's range stops short of the Sahara from South Sudan and southern Ethiopia extending south along eastern Africa, as far as Zambia, Mozambique, and Malawi, before spreading into most southern African countries. They are regionally extinct in Burundi and Lesotho, and they may have lived in Algeria in the Neolithic Era.^[18]
Plains zebras generally live in treeless grasslands and savanna woodlands^[9] but can be found in a variety of habitats, both tropical and temperate. However they are generally absent from deserts, dense rainforests and permanent wetlands.^[9] Zebras also live in elevations from sea level to 4,300 m on Mount Kenya. They rely on rainfall for food and water, and go on great migrations to follow the rains. The zebras will migrate up to 700 miles (1,100 km) for food. Other grazers also migrate. Plains zebras are highly water-dependent^[4] and are usually found within 25–30 kilometers of a water source.

Diet and predation

Zebras grazing with wildebeests in the Ngorongoro Crater

In one study, the zebra's diet was estimated to be 92% grass, 5% herbs, and 3% shrubs.^[19] Unlike many of the large ungulates of Africa, the plains zebra does not require (but still prefers) short grass to graze. It eats a wide range of different grasses, preferring young, fresh growth where available, and also browses on leaves and shoots from time to time. In consequence, it ranges more widely than many other species, even into woodlands, and it is often the first grazing species to appear in a well-vegetated area.^[4] Zebras have a simple stomach and use hindgut fermentation (caeco-colic), which allows them to digest and assimilate larger amounts of forage during a 24-hour period.^[20] Thus, zebras are less selective in foraging, but they do spend much time eating. The zebra is a pioneer grazer and prepares the way for more specialized grazers like blue wildebeests and Thomson's gazelles^[4] which depend on shorter and more nutritious grasses.
The plains zebra's major predators are lions and spotted hyenas.^[8] Nile crocodiles are also great threats during migratory river crossings. Wild dogs, cheetahs, and leopards also prey on zebras, although the threats they pose are generally minor and they mostly attack the foals. Olive Baboons may prey on foals, but pose no threat to adults. The zebra can be a formidable adversary, since they have a strong bite and a kick powerful enough to kill land predators. They often try to outrun larger predators such as lions and spotted hyenas, whereas they often stand their ground with the smaller predators.

Interactions with other grazers

Plains zebra herds will mix and migrate together along with other species such as wildebeests. Wildebeests and zebras generally coexist peacefully and will alert each other to predators. However, aggressive interactions occasionally occur.^[21][22]

Behavior

 

 

 

Social structure

A zebra harem in Etosha National Park

The plains zebra is highly social and usually forms small family groups called harems, which consist of a single stallion, several mares, and their recent offspring. The adult membership of a harem is highly stable, typically remaining together for months to years. Groups of all male "bachelors" also exist. These are stable groups of 2-15 males with an age-based hierarchy lead by a young male.^[4] These males stay in their groups until they are ready to start a harem. The bachelors prepare for their adult roles with play fights and greeting/challenge rituals, which take up most of their activities.^[4] Multiple harems and bachelor groups come together to form herds. Plains zebras are unusual among harem-holding species in forming these groups.^[23] In addition, pairs of harems may create temporarily stable subgroups within a herd, allowing individuals to interact with those outside their group.^[23] Among harem-holding species, this has only been observed in primates like the gelada and the hamadryas baboon.^[23]
Stallions form and expand their harems by abducting young mares from their natal harems.^[4][24] When a mare reaches sexual maturity, she will exhibit the estrous posture, which attracts nearby stallions,^[24] both bachelors and harem leaders. Her family stallion (likely her father) will chase off or fight stallions attempting to abduct her. Even after a young mare is isolated from her natal harem, the fight over her continues until her estrous cycle is over, and it starts again with the next estrous cycle.^[25] It is rare that the mare's original abductor keeps her for long.^[25] When the mare finally ovulates, the male that impregnates her keeps her for good. Thus, the mare becomes a permanent member of a new harem.^[25][26] The estrous posture of a female becomes less noticeable to outside males as she gets older, hence competition for older females is virtually non-existent.^[15]

Two zebras fighting

Mares exist in a hierarchy, with the alpha female being the first to mate with the stallion and being the one to lead the group. When new mares are added to the group, they are met with hostility by the other mares. Thus, the stallion must shield the new mares until the aggression subsides.^[4][26] The most recently added females rank lowest. Females that become unfit or weak may drop in their rank, though. The female membership of a harem stays intact even if a new stallion takes over.^[15] Zebras strengthen their social bonds with grooming. Members of a harem nip and scrape along the neck, shoulders, and back with their teeth and lips. Mothers and foals groom the most often, followed by siblings. Grooming shows social status and eases aggressive behavior.^[4]
A stallion will defend his group from other males. When challenged, the stallion issues a warning to the invader by rubbing nose or shoulder with him. If the warning is not heeded, a fight breaks out. Zebra fights often become very violent, with the animals biting at each other's necks, heads or legs, wrestling to the ground, and occasional kicking. Sometimes a stallion will lie still on the ground as if surrendering, but once the other male lets up, will strike and continue the fight.^[4] Most fighting occurs over young mares in estrus, and as long as a harem stallion is healthy, he will usually not be challenged. Only unhealthy stallions have their harems taken over, and even then the new stallion gradually takes over pushing the old one out without a fight.^[4]

Communication

 



At least six different calls have been documented for the plains zebra. One of which is its distinctive high-pitched contact call heard as "a-ha, a-ha, a-ha" or "kwa-ha, kaw-ha, ha, ha".^[15] When a predator is sighted, a zebra will make a two-syllable alarm call. A loud snort is made when moving in cover of potential danger. When in contentment, a zebra will make a more drawn-out snort. Males will make a short high-pitched squeal when hurt and foals will emit a drawn out wail when in distress.^[15] There are two main facial expressions made by zebras. One is for greeting and involves the ears sticking up and directed forward; the other is threatening and involves the ears down.^[15]

Reproduction

Mother zebra nursing her foal

The stallion mates with all his mares. Mares may give birth to one foal every twelve months. The birthing peak is during the rainy season. She nurses the foal for up to a year. The stallion is generally intolerant of foals that are not his. It is possible that zebras practice infanticide and feticide; such incidences have been observed in both captive individuals^[27] and in nature. In the film "Great Zebra Exodus," a mare was trying to protect her foal from a new stallion as its father was a fallen stallion.^[28] Like horses, zebras are able to stand, walk, run from danger, and suckle shortly after they are born. At the moment of birth, a mother zebra keeps any other zebra away from her foal, including the stallion, the other mares, and even the previous offspring. Later, though, they all bond. Within the group, a foal has the same rank as its mother.^[15] Plains zebra foals are protected by their mother as well as the head stallion and the other mares in their group. Even with parental protection, up to 50% of zebra foals are taken by predation, disease, and starvation each year.
Young male zebras eventually leave their family groups. This is not because of sexual maturity or being kicked out by their fathers, but because their relationship with their mothers have faded after the birth of a sibling.^[8][24] The young stallion then seeks out other young stallions for company.^[24] Young females may stay in the harem until they are abducted by another stallion.^[8]

Anti-predator behavior

 


For protection from land predators, the plains zebra retreats into open areas with good visibility at night. When the groups forage or sleep, one zebra will keep watch, and if a predator is spotted, it will bark or snort loudly.^[8] When being hunted by hyenas or wild dogs, a zebra harem stays close together and cooperates to protect threatened members,^[4] particularly the young. The harem stallion will go on the offensive and attack the dogs or hyenas.^[4] Though hyenas may harass the stallion, they usually only concentrate on the herd, and attempt to dodge the stallion's assaults. Unlike stallions, mares typically only react aggressively to hyenas or dogs when their foals are threatened. Unlike wildebeest, zebras rarely take to water when escaping hyenas.^[29] With lions, a zebra's best defense is to outpace them, as lions do not have as much endurance as hyenas or wild dogs. Cheetahs and leopards are mostly threats to foals, as an adult zebra is fully capable of driving them away.

Human interactions

 

 

Conservation

 Overall, the plains zebra population remains stable, and the species faces no major threat that would cause range-wide decline.^[1] The zebra can be found in numerous protected areas across its range, including the Serengeti National Park in Tanzania, Tsavo and Masai Mara in Kenya, Hwange National Park in Zimbabwe, Etosha National Park in Namibia, and Kruger National Park in South Africa. There are some stable populations in unprotected areas.^[1]

Some local populations, though, have faced great declines and even extinctions. Though facing decline in numbers the plains zebra population is thriving at about 750,000. One subspecies, the quagga, is now extinct. In Tanzania, the zebra population has decreased by 20% from the late 1990s to the mid-2000s.^[1] Zebras are threatened by hunting for their hide and meat, and habitat change from farming. They also compete with livestock for food,^[30][31] and are sometimes culled. Poaching is largely a threat to northern populations, while southern populations are threatened mostly by habitat loss. Recent civil wars in Rwanda, Somalia, South Sudan, Ethiopia, and Uganda have caused dramatic declines in all wildlife populations, including those of plains zebra. It is now extinct in Burundi. Civil war in Angola during much of the past 25 years has devastated its wildlife populations, including its once-abundant plains zebra, and destroyed the national parks administration and infrastructure.
Nevertheless, plains zebras are protected in most of their range. They are an important economic source in tourism.

In culture

The zebra is revered in some African cultures as a symbol of beauty. In the dances of the Karamojong tribe of Uganda, women would paint themselves in zebra stripes and act like them.^[8] The Dube tribe of South Africa features a zebra on its totem. Zebras also appear on the coat of arms of Botswana.

References

THE HAWAIIAN MONK SEAL

The Hawaiian monk seal, Neomonachus schauinslandi (formerly Monachus schauinslandi), is a highly endangered species of earless seal in the family Phocidae that is endemic to the Hawaiian Islands.^[2]
The Hawaiian monk seal is one of two remaining monk seal species; the other is the Mediterranean monk seal. A third species, the Caribbean monk seal, is extinct.^[3]
The Hawaiian monk seal is the only seal native to Hawaii, and, along with the Hawaiian Hoary Bat, is one of only two mammals endemic to the islands.^[4]
These monk seals are a conservation reliant endangered species. The small population of about 1,100 individuals is threatened by human encroachment, very low levels of genetic variation, entanglement in fishing nets, marine debris, disease, and past commercial hunting for skins. There are many methods of conservation biology when it comes to endangered species; translocation, captive care, habitat cleanup, and educating the public about the Hawaiian monk seal are some of the methods that can be employed.^[5][6][7]

 

 

Etymology

Known to native Hawaiians as ʻIlio-holo-i-ka-uaua, or "dog that runs in rough water", its scientific name is from Hugo Hermann Schauinsland, a German scientist who discovered a skull on Laysan Island in 1899.^[8] Its common name comes from short hairs on its head, said to resemble a monk.^[3] The Hawaiian monk seals are adopted to be Hawaii's state mammal.

Description

Its grey coat, white belly, and slender physique distinguish them from their cousin, the harbor seal (Phoca vitulina).^[3] The monk seal’s physique is ideal for hunting its prey: fish, lobster, octopus and squid in deep water coral beds.^[9] When it is not hunting and eating, it generally basks on the sandy beaches and volcanic rock of the Northwest Hawaiian Islands.^[10]
The Hawaiian monk seal is part of the family Phocidae, being named so for its characteristic lack of external ears and inability to rotate its hind flippers under the body.^[11] The Hawaiian monk seal has a relatively small, flat head with large black eyes, eight pairs of teeth, and short snouts with the nostril on top of the snout and vibrissae on each side.^[3] The nostrils are small vertical slits which close when the seal dives underwater. Additionally, their slender, torpedo-shaped body and hind flippers allow them to be very agile swimmers.^[12]
Adult males are 300 to 400 pounds (140 to 180 kg) in weight and 7 feet (2.1 m) in length while adult females tend to be, on average, slightly larger, at 400 to 600 pounds (180 to 270 kg) and 8 feet (2.4 m) in length. When monk seal pups are born, they average 30 to 40 pounds (14 to 18 kg) and 40 inches (1.0 m) in length. As they nurse for approximately six weeks, the grow considerably, eventually weighing between 150 to 200 pounds (68 to 91 kg) by the time they are weaned, while the mother loses up to 300 pounds (140 kg).
Monk seals, like elephant seals, shed their hair and the outer layer of their skin in an annual catastrophic molt. During the most active period of the molt, about 10 days for the Hawaiian monk seal,^[13] the seal remains on the beach. The hair, generally dark gray on the dorsal side and lighter silver ventrally, gradually changes color through the year with exposure to atmospheric conditions. Sunlight and seawater cause the dark gray to become brown and the light silver to become yellow-brown, while long periods of time spent in the water can also promote algae growth, giving many seals a green tinge. The juvenile coat of the monk seal, manifest in a molt by the time a pup is weaned is silver-gray; pups are born with black pelage. Many Hawaiian monk seals sport scars from shark attacks or entanglements with fishing gear. Maximum life expectancy is 25 to 30 years.

Evolution and migration

Hauled-out seal

The monk seals are members of the Phocidae. In an influential 1977 paper, Repenning and Ray proposed, based on certain unspecialized features, that they were the most primitive living seals.^[14] However, this idea has since been entirely superseded.
In an effort to inform the public and conserve the seals, the National Oceanic Atmospheric Administration (NOAA) Fisheries Service developed a historical timeline to demonstrate that the Hawaiian islands has been home to the seals for millions of years and that the seals belong there. Evidence points to monk seals migrating to Hawaii between 4-11 million years ago (mya) through an open water passage between North and South America called the Central American Seaway. The Isthmus of Panama closed the Seaway approximately 3 million years ago.^[15]
Berta and Sumich ask how this species came to the Hawaiian Islands when its closest relatives are on the other side of the world in the North Atlantic and Mediterranean Sea.^[16] The species may have evolved in the Pacific or Atlantic, but in either case, came to Hawaii long before the first Polynesians.

Ecology

Habitat

A Hawaiian monk seal observed in Kauai.

The majority of the Hawaiian monk seal population can be found around the Northwest Hawaiian Islands but a small and growing population lives around the main Hawaiian Islands.^[10] These seals spend two-thirds of their time at sea. Early studies (done at Midway Atoll) concluded that they frequently stayed inside the lagoons as opposed to the deep ocean, because of the larger abundance of fish found in their coral reefs.^[12] However, recent use of animal-born video imaging, temperature/depth recorders, and satellite telemetry has shown that monk seals actually spend much more time foraging in deeper water outside the reefs at subphotic depths of 300 metres (160 fathoms) or more.^[17][18] Hawaiian monk seals breed and haul-out on sand, corals, and volcanic rock; sandy beaches are more commonly used for pupping.^[10] Due to the immense distance separating the Hawaiian Islands from other land masses capable of supporting the Hawaiian monk seal, its habitat is limited to the Hawaiian Islands.

Feeding

Hawaiian monk seals mainly prey on reef dwelling bony fish, but they also prey on cephalopods, and crustaceans.^[9] Both juveniles and sub-adults prey more on smaller octopus species, such as Octopus leteus and O. hawaiiensis, nocturnal octopi species, and eels than the adult Hawaiian monk seals.^[9] While adult seals feed mostly on larger octopi species such as O. cyanea. Hawaiian monk seals have a broad and diverse diet due to foraging plasticity which allows them to be opportunistic predators that feed on a wide variety of available prey.^[9]

Predators

Tiger sharks and Galapagos sharks are both predators of the Hawaiian Monk Seal.^[19]

Behavior

Reproduction

Hawaiian monk seals mate in the water during their breeding season, which occurs between December and August.^[3] Females reach maturity at age four and bear one pup a year. The fetus takes nine months to develop, with birth occurring between March and June. Pups start around 16 kilograms (35 lb) and are about 1 metre (3 ft 3 in) long. They can have 1 baby pup a year.^[20]

Nursing

The pups are born on beaches and nursed for about six weeks. The mother does not eat or leave the pup while nursing. After that time, the mother deserts the pup, leaving it on its own, and returns to the sea to forage for the first time since the pup’s arrival.^[12]

Status

A Hawaiian monk seal observed on the North Shore of Oahu, near Waimea Bay.

Most seals are found on the Northwestern Hawaiian Islands.^[21]
The Hawaiian monk seal is critically endangered,^[22] although its cousin species the Mediterranean monk seal (M. monachus) is even rarer, and the Caribbean monk seal (M. tropicalis), last sighted in the 1950s, was officially declared extinct in June 2008.^[23] The total population of Hawaiian monk seals is in decline - the larger population that inhabits the northwest islands is declining while the smaller population on the main Hawaiian Islands is increasing.^[24][25] In 2010, it was estimated that only 1100 individuals remained.
Seals nearly disappeared from the main Hawaiian Islands, but the population has begun to recover. The growing population there was approximately 150 as of 2004.^[21] Individuals have been sighted in surf breaks and on beaches in Kauaʻi, Niʻihau and Maui. Community volunteers on Oʻahu have made many anecdotal blog reports of sightings around the island since 2008. In early June 2010, two seals hauled out on Oʻahu's popular Waikiki beach. Seals have hauled out at O'ahu's Turtle Bay,^[26] and again beached at Waikiki on March 4, 2011, by the Moana Hotel. Yet another adult came ashore for a rest next to the breakwater in Kapiolani Park Waikiki on the morning of 11 December 2012, after first being spotted traveling west along the reef break from the Aquarium side of the Park. In 2006, twelve pups were born in the main Hawaiian Islands, rising to thirteen in 2007, and eighteen in 2008. As of 2008 43 pups had been counted in the main Hawaiian islands.^[27] Since 2012 and possibly earlier, there have been many anecdotal reports of monk seals hauling out on O'ahu's Kaena Point.
The Hawaiian monk seal was officially designated as an endangered species on November 23, 1976, and is now protected by the Endangered Species Act and the Marine Mammal Protection Act. It is illegal to kill, capture or harass a Hawaiian monk seal. Even with these protections, human activity along Hawaii's fragile coastlines (and in the world at large) still provides many stressors.^[28]

Threats

Hawaiian monk seal

Natural factors threatening the Hawaiian monk seal include low juvenile survival rates, reduction of habitat/prey associated with environmental changes, increased male aggression, and subsequent skewed gender ratios.^[29] Anthropogenic or human impacts include hunting (during the 1800s and 1900s) and the resulting small gene pool, continuing human disturbance, entanglement in marine debris, and fishery interactions.^[29]

Natural threats

Low juvenile survival rates continue to threaten the species. High juvenile mortality is due to starvation and marine debris entanglement.^[6] Another contributor to the low juvenile survival rates is the predation from sharks, including tiger sharks. Most mature monk seals bear scars from shark encounters—many such attacks have been observed.^[29]
Reduced prey abundance can lead to starvation. A reduction in habitat associated with environmental changes is one cause.^[29] Habitat is shrinking due to erosion in the Northwest Hawaiian Islands, reducing the islands/beaches.^[29] Lobsters, the seals' preferred food other than fish, have been overfished. Competition from other apex predators such as sharks, jacks, and barracudas, leaves little for developing pups. The creation of Papahānaumokuākea Marine National Monument which encloses these islands may expand food supplies.
Mobbing is a practice among the seals that involves multiple males attacking one female in mating attempts. Mobbing is responsible for many deaths especially to females.^[30]
Mobbing leaves the targeted individual with wounds that increase vulnerability to septicemia, killing the victim via infection.^[30] Smaller populations were more likely to experience mobbing as a result of the higher male/female ratio and male aggression. Unbalanced sex-ratios were more likely to occur in slow-growing populations.^[31][32]
Further, postmortem examinations of some seal carcasses revealed gastric ulcerations caused by parasites.^[33]

Anthropogenic Impacts

In the nineteenth century, large numbers of seals were killed by whalers and sealers for meat, oil and skin.^[34] U.S. military forces hunted them during World War II, while occupying Laysan Island and Midway.^[34]
The Hawaiian monk seal has the lowest level of genetic variability among the 18 pinniped species.^[6] This low genetic variability was allegedly due to a population bottleneck caused by intense hunting in the 19th century.^[6] This limited genetic variability reduces the species ability to adapt to environmental pressures and limits natural selection thus increasing their risk of extinction.^[6] Given the monk seal's small population, the effects of disease could be disastrous.
Monk seals can be affected by the toxoplasmosis pathogen in cat feces that enters the ocean in polluted runoff and wastewater, a new phenomenon.^[35] Over the past ten years, toxoplasmosis killed at least four seals. Other human-introduced pathogens, including leptospirosis, have infected monk seals.^[35]
Human disturbances have had immense effects on the populations of the Hawaiian monk seal. Monk seals tend to avoid beaches where they are disturbed; after continual disturbance the seal may completely abandon the beach, thus reducing its habitat size, subsequently limiting population growth. For instance, large beach crowds and beach structures limit the seal’s habitat.^[5][29][35] Although the WWII military bases in the northwestern islands were closed, minimal human activities can be enough to disturb the species.^[29]
Marine fisheries can potentially interact with monk seals via direct and indirect relationships. Directly the seal can become snared by fishing equipment, entangled in discarded debris, and even feed on fish refuse.^[29]
Entanglement can result in mortality because the seals get trapped in marine debris such as fishing nets and cannot maneuver or even reach the surface to breathe.^[6] International law prohibits the intentional discarding of debris from ships at sea. Monk seals have one of the highest documented rates of entanglement of any pinniped species.^[29]

Conservation

 

Reversing the population decline hinges on a comprehensive, scientifically sound characterization and mitigation of relevant natural and anthropogenic factors along with better understanding of the species' particular vulnerabilities.^[29]
Genetic data analysis is needed because identifying individuals genetically along with confirming maternity and paternity can provide information about male and female reproductive rates which are crucial to wildlife managers.^[7]
In 1909, President Theodore Roosevelt created the Hawaiian Islands Reservation that included the Northwest Hawaiian islands. The Reservation later became the Hawaiian Islands National Wildlife Refuge (HINWR) and moved under the jurisdiction of the U.S. Fish and Wildlife Service (USFWS).^[29] Throughout the 1980s, the National Marine Fisheries Service completed various versions of an Environmental Impact Statement that designated the Northwest Hawaiian Islands as a critical habitat for the Hawaiian monk seal. The designation prohibited lobster fishing in waters less than 10 fathoms in the Northwest Hawaiian Islands and within 20 nautical miles of Laysan Island. The National Marine Fisheries Service designated all beach areas, lagoon waters, and ocean waters out to a depth of 10 fathoms (later 20 fathoms) around the Northwestern Hawaiian Islands, except for one of the Midway group, Sand Island. In 2006, a Presidential Proclamation established the Papahanaumokuakea Marine National Monument, which incorporated the Northwestern Hawaiian Islands Coral Reef Ecosystem Reserve, the Midway Atoll National Wildlife Refuge, the Hawaiian Islands National Wildlife Refuge, and the Battle of Midway National Memorial, thus creating the largest marine protected area in the world and affording the Hawaiian monk seal further protection.^[36]
NOAA cultivated a network of volunteers to protect the seals while they bask or bear and nurse their young. NOAA is funding considerable research on seal population dynamics and health in conjunction with the Marine Mammal Center.
From NOAA, several programs and networks were formed in order monk seal. Community programs such as PIRO have helped to improve community standards for the Hawaiian monk seal. The program also creates networks with the Native Hawaiians on the island to network more people in the fight for conservation of the seals. The Marine Mammal Response Network (MMRN) is partnered with NOAA and several other government agencies that deal with land and marine wildlife.^[37]
The Recovery Plan for the Hawaiian Monk Seal identifies public outreach and education as a key action for promoting the conservation of the Hawaiian monk seal and its habitat.^[36]
To raise awareness of the species' plight, on June 11, 2008, a state law designated the Hawaiian monk seal as Hawaii's official State Mammal .^[38]
The task is to identify a manner of alleviation that is possible, cost-effective, and likely to maximize the organic return (in terms of growth potential) until much time has passed and natural conditions allow scientists to observe the effects. .^[39]

Protecting female pups

One key natural factor affecting the seal populations is the male-biased sex-ratio, which results in increased aggressive behaviors such as mobbing.^[31] These aggressive behaviors decrease the number of females in the population. Two programs effectively aid female survival rates.
Project “Headstart” began in 1981, collected and tagged female pups after weaning, and placed them in a large, enclosed water and beach area with food and lacking disturbances.^[40] The female pups remain during the summer months, leaving at roughly age three to seven months.
Another project began in 1984 at French Frigate Shoals. It collected severely underweight female pups, placed them in protective care and fed them. The pups were released as yearlings and relocated to the Kure Atoll.^[40]
Some habitats are better suited to increase survival probability making relocation a popular and promising method.^[7] Although no direct links between infectious diseases and seal mortality rates have been found, unidentified infectious diseases could prove detrimental to relocation strategies.^[41] Identification and mitigation of these and other possible factors (e.g., disease) limiting population growth represent ongoing challenges and are the primary objectives of the Hawaiian monk seal conservation and recovery effort.^[33]
It is also important to consider the mothers who nurse their (female and male) pups. Seal milk is very rich in nutrients which also allows pups to gain weight rapidly. With the rich milk from the mother the pup is more prone to quadruple their initial weight before weaning. The mother seal also loses a tremendous amount of weight while nursing.^[42]

Draft environment impact statement

In 2011, the National Marine Fisheries Service issued a controversial draft programmatic environmental impact statement intended to improve protections for the monk seal.^[43] The plan includes:

• Expanded surveys using technology such as remote cameras and unmanned, remotely operated aircraft.

• Vaccination studies and vaccination programs.

• De-worming program to improve juvenile survival.

• Relocation to the Northwestern Hawaiian Islands.

• Diet supplements at feeding stations in the Northwestern Hawaiian Islands.

• Tools to modify undesirable contact with people and fishing gear in the main Hawaiian Islands.

• Chemical alteration of aggressive monk seal behavior.