Platypus project

By Peter Petersen

In 2014 I started the Platypus Project shortly after I began working in the National Aquarium of Denmark: Den Blaa Planet. The goal is to learn as much as possible about the Platypus and how to keep and breed them and best inspire to their conservation.

This Platypus (Ornithorhynchus anatinus) just surfaced in Meander river near the town of Deloraine, Tasmania. This photo was taken on my trip in January 2019.

Conservation starts with getting peoples hearts to beat for the animals of the underwater world. This is a platypus encounter at Healesville Sanctuary where people can get up close an personal with these remarkable animals.  

The platypus chooses whether or not if it will participate in the encounter. But usually they will. Because there is a food reward at stake.  

 

Natural geographic range:

 

The Platypus (Ornithorhynchus anatinus) inhabits the east coast of Australia from the base of Cape York Peninsula and all the way down to Tasmania. It is considered Near Threatened by IUCN and populations are decreasing.

 The main reasons for the decline is polution, droughts, stream regulation, and extraction of water for agricultural, domestic, and industrial supplies. But also predation by the introduced Red Fox, dogs and cats and entanglement in or ingestion of plastic, rubber and metal litter.

Etymology

The name Platypus is derived from Greek, meaning: flat-footed. The scientific name is derived from Greek and Latin. The genus Ornithorhynchus means: Bird snout (greek). The species name: anatinus, meaning: duck-like (Latin). 

Classification

The 4 species of Echidna and the platypus (Monotremata) are the only types of living mammals which lay eggs. Platypus belong to the family Ornithorhynchidae.

Size

Males are usually around 50 cm when fully grown (max. reported lenght is 80 cm). The female is around 43 cm. Animals from the northern range are usually smaller then the Tasmanian population. Platypus in Tasmania can be three times larger the ones in the rest of Australia. Platypus can weight 1-10 kilos. Average males are 2.4 kilos and females 0.7-1.6 kilos in some regions in the south. Northern animals are normally 1,4-1,5 kg for males and up to 0.9 kg for females depending on sources as well.

I have measured animals from natural history museums and they seem to have an average of 50 cm for males and and 48 cm for females. Photo above is from Natural History Museum in Copenhagen (Denmark)

Age

Average age: 7-12 years (in the wild). In captivity 17 years. Maximum age 21-26 years (Rare).

Anatomy

 

Bill

Platypus have 40.000 electroreceptors which are located in rostrocaudal rows in the skin of the bill. These receptors detect the electrical impulses that their prey produce and allow the platypus to track with extreme accurasy. For comparison the Long-billed echidna have 2.000 and the Short-billed echidna have only 400. Monotremes are the only mammals that use electroreception to find prey.

The platypus also have 60,000 mechanoreceptors for detecting vibrations in the water. Photo below is from Natural History Museum in Copenhagen (Denmark) specimen no. 34.

The platypus bill is soft. Below you can see the bill from the underside. The photo is from Natural History Museum in Copenhagen (Denmark) specimen no. 25 from 10/11-1917

The photo below is from Natural History Museum in Copenhagen (Denmark) specimen no. 25 from 10/11-1917

Below you can see the grooves in the bottom part of the bill. Photo taken in Natural History Museum in Copenhagen (Denmark) specimen no. 34

Platypus have cheek pouches in which food is stored until it can be chewed. Photo below is from Natural History Museum in Copenhagen (Denmark) 

Photo below taken in Natural History Museum in Copenhagen (Denmark) specimen no. 24 (female) from 14/2-1917

Male on the left and female on the right. The photo below is from Natural History Museum in Copenhagen (Denmark).

Tail

The platypus uses its tail for storage of fat reserves. The tail is also used for collecting nesting materials.

The underside of a male platypus tail from Natural History Museum in Copenhagen (Denmark) specimen no. 11 from 31/12-1869

The tail seen from above from Natural History Museum in Copenhagen (Denmark) specimen no. 11 from 31/12-1869

The tail seen from above from Natural History Museum in Copenhagen (Denmark) specimen no. 25 from 10/11-1917. The fur is more coarse on the upper side of tail.

The tail seen from below from Natural History Museum in Copenhagen (Denmark) specimen no. 24 from 14/2-1917 (female). The fur is more smooth on the under side of tail.

Comparing the specimens from museums, zoos and from the wild, I would say that the tails of females seem to be shorter and wider than the males. Photo above is from Natural History Museum in Copenhagen (Denmark) specimen no. 4 (in the middle) from 30/8-1879 is a male.

Fur

Its fur traps a layer of insulating air to keep the animal warm.

The fur on the back of a platypus from Natural History Museum in Copenhagen (Denmark) specimen no. 29 from 22/4-1936

The fur from the belly of a platypus from Natural History Museum in Copenhagen (Denmark) specimen no. 29 from 22/4-1936 

Teeth

Platypus have teeth when they are young (milk teeth), which are shed before the animal becomes an adult, and are replaced by horny pads. When the platypus hatch they have an egg-tooth to help them break through the shell.

Above you can see a horny pad on a underjaw bone. The photo is from Natural History Museum in Copenhagen (Denmark) specimen no. 11 from 31/12-1869.

Above you can see the skull with the upper horny pads. The photo is from Natural History Museum in Copenhagen (Denmark) specimen no. 32 from Richmond river in the middle of the platypuses natural distribution range.  

Ears

They have no external ears but can hear through the ear holes, when they are above water. When submerged they close their ears. Photo of 0.7 cm earbone below is from Natural History Museum in Copenhagen (Denmark) specimen no. 11 from 31/12-1861

Spurs

Males have a sharp, movable, horny, poison “spur” on the inner side of each hind limb near the heel. It is about 15 mm. Photo below is from Natural History Museum in Copenhagen (Denmark) specimen no. 11 from 31/12-1861.

Close up this is what the spur looks like. Photo below is from Natural History Museum in Copenhagen (Denmark) specimen no. 11 from 31/12-1861.

 

The female spurs have no function and she loses them before she reaches 1 year of age. Below you see and male and female hind leg for comparison. Photo below is from Natural History Museum in Copenhagen (Denmark).

The spures on the male is not always visible underneath the dense fur. Photo below is from Natural History Museum in Copenhagen (Denmark).

Front legs

Front legs have no spures. Photo below is from Natural History Museum in Copenhagen (Denmark) specimen no. 11 from 31/12-1861.

Photo below is from Natural History Museum in Copenhagen (Denmark) specimen no. 1.

Photo below is a platypus front leg from Natural History Museum in Copenhagen (Denmark) specimen no. 25 from 10/11-1917.

Venom

The venom from a platypus is relatively weak compared to others and is not deadly to humans. It does, however, cause excruciating pain, which does not respond to treatment with morphine. There’ve been no recorded human fatalities. Worst case I could find was with a 57-year-old man who got spurred and his hand stayed weak and hypersensitive to pain for three months after his “spurring”. But it is known to have killed smaller dogs.

The venom is composed largely of defensin-like proteins (DLPs). It consists of 83 toxins. One of the proteins are Culprit which lower the victims blood pressure others resembles known neurotoxins.

In late winter males’ testicles swell, they start fighting over the females, and when they fight, they wrap their legs around their opponent and inject each other with venom through the spurs. Venom made by their crural glands that swells with about a 5-10 ml volume of venom during mating seasons. The loser collapse, its limbs paralyzed, while the winner went off to be breed. The loser would eventually recover and swim off again.

Milky pores

The platypus's milk seeps through pores in its abdomen, not through teats as in all other mammals.

Eggs

The eggs have a soft shell like reptile eggs.

Cloaca

Monotremes have only one opening thats serves as digestive, reproductive, and urinary tract.  

Eyes

In recent studies it has been suggested that the eyes of the platypus are more similar to those of Pacific hagfish or Northern Hemisphere lampreys than other mammals.

This photo is from a river a Tasmania. Even though it was almost dark this male platypus kept an eye on me every time he surfaced. He was very curious and often came within 3-4 meters of me but always with open eyes and ear holes. He was on alert. 

Temperature 

Platypus live from tropical rainforest to thick ice and example from their most diverse biotope temperatures is Tasmania. Here the air temperatures are between -4 to 31 C and water temperature between  0-29 C. Burrow temperatures in summer around 17.5 C (22.8 C) and winter 14.2 C (12.2 C).  

Habitat

A Platypus habitat in the central Tasmania. Habitats are very diverse. They seem to be common in both fast flowing rivers and slow moving streams. Even still water lakes.

The Platypus (Ornithorhynchus anatinus) in this lake in Victoria were very shy. When they came to the surface they quickly dissappeared again even if we just made a small sound.  

A shallow habitat in central Tasmania.

Food

 Platypus prey on crustaceans (shrimps, crabs and crayfish also called yabby), annelid worms, water insects, insect larvae, clams, snails, little fish, frogs and tadpoles. They have a high metabolism. Eating approx. 20-50% of their body weight every single day.

Yabbies (Cherax destructor) are a freshwater crayfish and one of the main food items of Platypus. Used by both Melbourne Zoo and Healesville Sanctuary in Victoria, Australia.

Also the Australian earthworms (Anisochaeta dorsalis) are an important food source here shown by a Platypus keeper in Melbourne Zoo.

Mealworms (Tenebrio molitor) and pupa of the housefly (Musca domestica) is also part of the platypus diet at many Australian Zoos. The mealworms are gut loaded with an insectivore mix.

Platypus are very active animals and the prey on even the smallest worms. Thats why both Melbourne Zoo and Healesville Sanctuary use Blackworms (Lumbriculus variegatus) as a supplement. Food rations for a grown platypus could look like this:

Food Item Amount Unit
Fly Pupa 1/2-1/4 scoop
Mealworms 70-120  grams
Earthworms 100-200  grams
Blackworms 0-60 grams 
Yabbies Ad libitum Ad libitum 

In Melbourne zoo the male platypus gets a total of 730 grams food pr. day.  

Animals seen in platypus enclosures: 

 This young Gippsland water dragon (Intellagama lesueurii howittii) grow to around 60-100 cm TL. They eat fruit and insects near the water. They can stay submerged for up to 90 minutes. The photo was taken in Healesville Sanctuary. 

This is an semi adult Gippsland water dragon (Intellagama lesueurii howittii). 

Animals seen in natural platypus habitat

The endangered Southern bell frog (Ranoidea raniformis) at the Meander river near the town of Deloraine, Tasmania.

 

 

The Tasmanian Native-Hens (Tribonyx mortierii) diet mostly consists of grass shoots and the leaves of low herbs which it grazes during daylight hours. This photo was taken in Craddle mountain in Tasmania.

European Perch (Perca fluviatilis) is an invasive species introduced here in 1861. The Perch is considered a pest as it eats all the small native fish. This photo was taken in the Meander river near the town of Deloraine, Tasmania.

Another invasive species is the Brown Trout (Salmo trutta). This species was introduced from the United Kingdom in 1864. The predator is also foraging on the small native fish. This photo is from Victoria, Australia.

The Little Pied Cormorant (Microcarbo melanoleucos) seem to follow the platypus sometimes. Possibly to catch the fish they scare up from the bottom while feeding on yabbies. This photo was taken in Victoria.

The Superb Fairywren (Malurus cyaneus) is common around the rivers where I found platypus. Usually in the water grass and building nests. This is a male from near Meander river in Tasmania. 

 Other animals in platypus habitats

Kingfishers, Whiteheaded heron, water snakes, water rat.

Foraging

The platypus feeds by neither sight nor smell,closing its eyes, ears, and nose each time it dives. Adult platypuses do not have teeth, so bits of gravel help them to "chew" their meal. The photo above is from Meander river in Tasmania. 

 

A normal surface-time is 10-18 seconds. I made these videos in Meander river in Tasmania.

 

A standard dive is usually between 40-51 seconds. 

 

Enclosure

This is part of a platypus enclosure in Healesville sanctuary. This enclosure was connected to others by a complex of tunnels both for breeding burrows and for enrichment. Looking at the habitat of platypus and the enclosures of the zoos with breeding succes in these animals and enclosure should have:Pebbles and bolders for them to turn with their beaks in search for food. Larger rocks, roots, sand, leaves. Moving Clear water with small streams and waterfalls. Pools in different elevations. Areas with shallow water and fast current and still water areas as well. Plants like tree ferns, Iris and Alocasia. Loose soil and a complex of tunnels for burrows and the posibility for them to dig their own breeding burrows. 

Platypus night enclosure at Healesville Sanctuary. Notice the light is coming from the underwater and in front which make the lighting perfect to watch Platypus swimming. Completely without disturbing the animals as they close their eyes when submerged. 

Enrichment

Ideas for daily platypus enrichment provided by zoos I have visited: Reverse water flow, stop water flow, feed wild invertebrates, move furniture, change substrate, adding foreign objects to the enclosure, using misters and foggers, introducing floating fruits, introducing duckweed, using powerhead and/or bubbles, adding floating pool toys to the enclosure, browse tethered underwater, adding night sounds/new sounds, feeding blackworms and Tubifex, lowering the water level, adding tree fern trunk, feeding frozen bloodworms (4 cubes each), Adding grass tussocks, adding dry logs, adding leaves, feeding crickets, feeding glass shrimp, adding bark, scattered feedings, swaping bedding, adding small amounts of the diet on display and feeding mealworms on floating bark.

Activity 

Varies a lot. Some hunt in daylight while others only eat at night. They normally always come out in the afternoon in their search for food. Some swim 1 kilometer or more up and down the river while others only stay in one little pool. But they are not migrating animals.  

Gestation period

10-14 days

Litter size

Between 1 and 4 eggs pr. year (normally 2 eggs).

Breeding

Platypus were first bred in captivity in 1943 by David Fleay at Healesville sanctuary (Zoo Victoria). The first was a female called Corrie (parents named Jack and Jill). In 1955 she escaped in to Badger Creek and was never found.

Next succesfull breeding was 47 years later in Warrawong Sanctuary (1991). In 1999 Healesville sanctuary got 2 male-twins. In 2002 the female twins Samantha and Binari hatched in Taronga Zoo in Sydney.

 Breeding and sleeping burrow

The entrance of the burrow is right above or in the surface. Sometimes it can be as far as 2-3 meters above the surface to prevent the cave from flooding. The female builds the nest and collects leaves for the cave. She hides them under her tail while she collects more.

The photo above is from Meander river in Tasmania. In between the roots in the left side of the photo a platypus had a burrow. I watched this platypus for several days and documented its behavior. This specimen came out every day at around 17 o'clock and were active all night until around 7-8 o'clock in the morning when it came back to its burrow.  

Nesting

Platypus use grass and leaves for nesting. Sword tussock-grass (Poa ensiformis), Eucalyptus leaves and Basket grass (Lomandra longifolia) seem to be among their favorite nestings materials. This photo (above) of Basket grass is from Victoria.

 

Husbandry

Surveillance cameras and accessability of the entire tunnelssystem is in my opinion crucial to husbandry of these animals. This photo is from Healesville Sanctuary.

Handling

Hold in the tip of the tail. Be careful with the spurs (in males) on the hind limbs. Only experienced keepers should handle these animals.

If carefull spurring is rare. In Melbourne Zoo they have had only 1 case in 35 years and the keeper did not need pain relief. 

Behaviour observations

Naked spots on the tail of the females are often associated repetitive mating and is quit normal. The fur is worn off.

Males either avoid each other or fight (only in mating season) when they meet in the river. Platypus are largely solitary animals.

When not foraging in water they normally occupy a resting or nesting burrow in earth banks.

Diseases

Populations in Tasmania are affected by mucormycosis (associated with the fungal pathogen Mucor amphibiorum). It might be possible to avoid problems with this disease by filtering the water through UVC to bring down the total number of disease agents.

The tick (Ixodes ornithorhynchi) lives only on platypus. 

Platypus use a lot of time grooming their fur to make sure its 100% waterproof. In my observations they groom every fifth time they surface in average. The could be a behavior to keep an eye on in captivity. To make sure they show natural behavior. This photo is from Meander river in Tasmania.

 

Body temperature and health

Healthy animals have a body temperature of 32 degrees C. Platypus have 5X and 5Y chromosomes. Platypus are sensitive towards phosphate (PO4). Often water change and good filtration is crucial (Filters can never be too big). I would recommend using UVC to lower the amount of disease agents in the water. Platypus do not seem to be affected by neither GH, KH and pH values (in the normal range).

The photo of the sandfilter above is from Melbourne Zoos Platypus enclosure. They currently keep one male (at this point in time).

Rising levels of Phosfate (PO4) in the rivers might be the reason for platypus decline in some areas. This photo is from Meander river in Tasmania.

Sleep

Platypus normally sleep for 8-9 hours a day (average). They always sleep in their burrow. This box in the photo above is an example of a "burrow" from a zoo in Australia. Most zoos have advanced tunnelsystems which leads to a box (sleeping quarters). This box should have a locking mechanism and be moveable to make it easier for the keeper to transport the platypus without stressing the animal.

It also makes it possible to weigh the animals on a regular basis to make sure they dont loose or gain to much weight.

 

A special thanks to: 

Zoos Victoria (Australia)

Dr. Jenny Gray (CEO)

Healesville Sanctuary, Zoos Victoria (Australia)

Falk Wicker (Life Science Manager Enrichment)

Natasha "Tash" Rose (Zookeeper)

Jessica Thomas (Keeper Life Sciences) 

Dr. Rupert Baker (General Manager, HS Life Sciences) 

Melbourne Zoo, Zoos Victoria (Australia)

Meagan Thomas (Life Science Coordinator and Zoo Keeper) 

Megan Richardson (Senior Animal keeper at Melbourne Zoo)

 Odense Zoo (Denmark)

Bjarne Klausen (M.Sc, MBA, CEO)

University of Copenhagen Natural History Museum in Copenhagen (Denmark)

Henrik Carl (Academic staff)

Peter Rask Møller (Associate Professor) 

Daniel Klingberg Johansson (Collection Manager for Mammology and Herpetology)

Environmental consultant and natural heritage (Tasmania)

Alex Dudley