Hawaiian Monk Seal and Ciguatoxin
Hawaiian Monk Seals, whose population has dwindled to around 1100, are now exposed to another threat. Researchers from NOAA have discovered a potent and highly-debilitating toxin in the critically endangered Hawaiian Monk Seal. The dangerous toxin, called ciguatoxin, is produced by marine algae common on coral reefs, and accumulates in fish species that are consumed by humans.
The study was conducted by marine toxin experts at NOAA’s National Ocean Service in collaboration with veterinarians and ecologists at NOAA’s National Marine Fisheries Service. Monk seals were sampled throughout the Hawaiian Islands, including in the Papahānaumokuākea Marine National Monument, and samples were analyzed for toxins.
The study reveals that Hawaiian Monk Seals (Monachus schauinslandi) are exposed to significant levels of these ciguatoxins. Ciguatera, the human disease caused by ciguatoxin, affects thousands of people every year worldwide and comes in the form of acute gastrointestinal and neurological illness with symptoms resembling chronic fatigue syndrome.
The threat could pose management challenges for this species that has been dwindling at four percent annually. “Based upon this study, we believe that ciguatoxin exposure is common in the monk seal population. This study is an important first step. However, we still need to understand more clearly how widespread exposure is and more importantly what role it may be playing in the decline of the species.”
Hawaiian Monk Seal and Threats
Hawaiian Monk Seals face a new threat from a pathogen in cat feces that is carried to the ocean in polluted runoff and sewage. Experts worry that the disease, toxoplasmosis, will derail efforts to restore this endangered species. Over the past ten years, the cat parasite has killed at least four monk seals in the main Hawaiian islands – two from Kauai, one from Oahu, one from Molokai, and perhaps more. In the past decade, toxoplasmosis has been regularly found in a wide range of marine mammals, including whales, dolphins, as well as seabirds, and the endangered Hawaiian crow.
No studies have been done in Hawaii, but in California, researchers have found that it infects sea otters mainly though runoff from urban areas. Flushing cat litter down the toilet is one pathway, since sewage treatment does not always kill the parasite’s hardy eggs, called oocysts. Studies have found that oocysts can live for at least two years in sea water.
Although domestic cats are considered the main source, feral cats in remote areas also transmit the disease. Nearly 40 percent of cats captured from the slopes of Mauna Kea, on the island of Hawaii, tested positive for toxoplasmosis. The state Division of Forestry and Wildlife estimates that 300,000 to 400,000 free-ranging cats live on Maui alone.
The Hawaiian Monk Seal (Monachus schauinslandi) is considered the most endangered pinniped in the United States. Their overall population is declining at a rate of about 4.5 percent a year. The good news is that in recent years, their numbers have been growing in the main Hawaiian islands. With only about 1,100 monk seals left in the wild, each death is very concerning, and now toxoplasmosis is one of the primary concerns. To raise public awareness about toxoplasmosis and cat feces, NOAA has begun talking with the Hawaii Humane Society, various interest groups, and the health department.
Hawaiian Birds and Nene Breeding
On Hawai‘i and Maui, Nene nest in higher elevation habitats, while most Nene on Kaua‘i nest and live in areas of managed grass at low elevations where populations were reintroduced. Some are starting to occupy upland areas of managed grass in Koke‘e State Park and are occasionally seen in bogs of Alaka‘i Swamp. Nene (Branta sandvicensis) mainly graze leaves, berries, seeds, fruits, and flowers of at least 50 species of native and alien plants, mainly grasses, herbs, and shrubs. Nene disperse seeds of some plant species utilized as food, thereby playing a potentially important role in successional ecosystems.
Vocalizations consist of two types of calls – low murmuring or nay-nay, and louder, more strident calls. Nene calls are performed in several contexts, including social signals involving family members, alarm calls and hissing involving predators and conspecifics, and calls before and during flight. Females also produce soft purring sound when contented.
Goslings give four calls – a Pleasure Call is given softly as family feeds, preens, or moves together and helps maintain contact among family members. A louder Greeting Call serves to maintain contact and recognition of family members. A Sleepy Call when tired helps synchronize rest periods. And a loud, high-pitched Distress Call is given when lost, cold, hungry, or when predators or other threats approach.
Nene pair with one mate, usually for life. Courtship displays include male walking ahead of female, showing his white undertail. After female accepts male, pair perform mutual Triumph Ceremony, an important part of courtship in which male threatens or attacks opponents, runs back to female, and calls loudly. Pair then call or cackle nearly into each other’s ears and make intermittent sideways and vertical head movements generally directed toward opponents.
Nest construction begins with the female selecting a site, usually in area near where she was hatched, reared, or fledged. Nests are generally oriented to avoid strong winds, direct sunlight, and rain. She scrapes shallow bowl in loose substrate with feet and lines bowl first with vegetation. While laying eggs, she adds feathers from her upper abdomen and lower breast.
As is characteristic of waterfowl endemic to remote islands, Nene produce very large, heavy eggs, with an average clutch size of three eggs. Only the female incubates, with the male guarding the female while on nest and during incubation recesses. Goslings develop adult plumage more quickly than other geese, becoming indistinguishable from adults at 4 to 5 months of age. Photo by Jack Jeffrey.
Humpback Whale Song Communication
Humpback Whales create several kinds of sounds to communicate with each other. There are social sounds, communicative sounds between mothers and calves, the feeding siren done in the feeding grounds, and the classic whale songs. In the 1950′s, their singing was discovered when the United States Navy experimented with hydrophones.
Social sounds are short, quick sounds which can hardly be heard under water with the human ear. These sounds can only be picked up with special hydrophones which would have to be close to the whales and pointed directly at them. The social sounds are used to communicate, especially when they travel slowly on the surface or when resting – but not when traveling at higher speeds. The majority of this kind of communication (85%) takes place between mothers and their calves, but also whales within a group communicating with each other.
It has been defined that only Humpback males are singing. Humpback Whales (Megaptera novaeangliae) go to a depth of between 40 and 130 feet and usually get into a certain position with their head downward, and remain motionless when they sing. Unlike a pop song with a melody, a whale song is more like a string of different sounds in different pitches that can sound like humming, snoring, groaning, sighing, or chirping. Similar to classical music, a whalesong consists of different themes which develop and build over the years. The whale songs can even be heard from a distance of 100 miles or more. The whales are singing mainly in their breeding grounds or on the way from or to their feeding grounds in cooler waters.
Hawaiian Reef Fish and Potter’s Angelfish
The Potter’s Angelfish (Centropyge potteri) is one of the the most commonly seen Hawaiian reef fish. This endemic fish gained its scientific species name (potteri) after former Waikiki Aquarium director Frederick Potter who ran the aquarium from its founding in 1903 to 1940.
It grows up to 5 inches in length, and is rusty orange overall darkening to a blackish-blue color below. The bluish colors are more pronounced in males, and the females show more orange. They have many irregular, grayish-blue vertical lines running the length of the body. The edges of the rear fins are striped horizontally with bright blue and black. The Potter’s Angelfish is usually seen in pairs or in small groups of a male and several females in clear water at depths of 10 to 150 feet under ledges or on reef slopes with plenty of shelter holes.
Hawaiian Reef Fish and Flame Angelfish
The Flame Angelfish is bright red in color with dark black bars running vertically down its body. This visually striking angelfish also has purple at its rear fins, which is more prominent in males. Flame Angelfish (Centropyge loriculus) grow to be 2 to 4 inches, and are relatively rare in Hawaiian waters. They are sometimes seen in shallow waters, but are more commonly seen below 60 feet deep among finger coral. Flame Angelfish eat filamentous algae, and are often seen repeatedly within a relatively small area.
Flame Angelfish are protogynous synchronous hermaphrodites meaning the all start off as unsexed and develop into fully functioning females and later have the potential to change into a male should no other males be available. There are no visible differences between males and females, and they form small harems between three to seven individuals when it’s time to spawn.
