Last year I was lucky enough to spend several months volunteering with the Mauritian Wildlife Foundation (MWF), where I worked on conservation projects with two endangered passerines; the Mauritus Olive white-eye, and Mauritius Fody. Whilst there I got the chance to work on other conservation projects, including the reptile recovery programme. Mauritius was once home to one of the world’s richest reptile diversities. Following the island’s colonisation in the 16th century many non-native species were introduced and most of the native forests were destroyed. Today, only 2% native forest cover on the “mainland” remains. Over a dozen native bird species, including the famed Dodo, as well as several reptiles and numerous plants were driven to extinction. Despite the loss of more than 60% of Mauritian reptile species, some managed to survive on one or a few of the offshore islands. One of these islands is Ile aux Aigrettes, where I lived and worked for over six months.
Ile aux Aigrettes is a small lagoon island where conservation activities have been ongoing since the 1980s to restore the endangered fauna and flora of Mauritius. The restoration work involved weeding of non-native invasive plants, as well as the eradication of introduced predators such as rats and cats. After the re-establishment of native forest, MWF began the translocation of endemic reptiles, such as Telfair’s skink and Gunther’s gecko. The indigenous (and charismatic) Ornate day gecko occurs still on the island naturally. More recently, Aldabra Giant Tortoises, native to the Seychelles, were introduced as they are genetically and ecologically similar to the (now extinct) tortoises that once inhabited the island. Tortoises play a key role in the ecosystem as grazers, browsers and seed dispersers.
After arriving in Mauritius I took a short boat trip from the mainland to the island off the southeast coast. Despite feeling a little jet-lagged, once I stepped onto the jetty my excitement began to build. As I made my way through the forest to the field station, an Aldabra tortoise ambled out in front of me. Now, before this encounter, the only time I ever saw a giant tortoise was at the Galapagos tortoise enclosure in London Zoo. This was a completely surreal moment for me, all I could do was stop and stare at this magnificent creature. As the days went on I soon befriended this tortoise known as “MT7”, he always napped right in front of the station! He is one of 20 free-roaming adult tortoises on the island, plus there was about 15 baby tortoises in a nursery at that time. Not long after my arrival I was asked to help with the annual tortoise survey, I of course jumped at the opportunity! The survey involves PIT tagging, taking morphometric measurements and weight, as well as health and disease screening.
This required a lot of heavy lifting, bringing the tortoises to and from the field station. Once there, we took stool and urine samples, that was the easy (and by far the messiest) part! The baby tortoises were then weighed, and measurements of the straight and curved carapace lengths were recorded. Blood samples were then taken; these are used for disease screening and DNA analysis. Every adult tortoise on the island is individually recognisable from its unique PIT tag code. The PIT tag is a tiny transponder that is surgically implanted under the skin and transmits a unique bar code when an electronic reader is passed over it. The larger baby tortoises were PIT tagged, so that they are easily identifiable for future surveys. All tortoises are painted with an ID number on their carapace. This is useful for monitoring an individual’s distribution over the island and for census purposes.
Day to day duties involved feeding the tortoises in the nursery. Their diet comprises of a variety of Mauritian fruit and veg, as well as endemic plants such as Hibiscus, which is their favourite by far! The tortoises are fed once a day and their water is changed daily. Other tasks included recording sightings of the adult tortoises. Every time I saw a tortoise roaming in the forest I would make a note of its ID and its location, this data is then entered into the tortoise log book. Over time this information can be used to generate a map of the tortoises distribution over the island, as well as providing an insight into their preferred habitats. As the adults are free-roaming they are able to breed naturally. They can breed all year round, and the females lay their eggs in sand-pits especially designed for this purpose. I was fortunate enough to find one baby tortoise in my time on Ile aux Aigrettes. I was in the middle of searching for Olive white-eye nests when I heard a rustling on the forest floor. I stooped down to peer through the undergrowth when out stumbled a baby tortoise. Needless to say I was delighted with my find! I picked up the tortoise and brought it to the nursery to join the others. When they reach a large size, the baby tortoises are taken from the island to the Gerald Durrell Endemic Wildlife Sanctuary (GDEWS) on the mainland, where they are reared in safety until their release back into the wild.
As I mentioned, endemic reptiles such as Telfair’s skink and Gunther’s gecko were recently introduced to Ile aux Aigrettes. Telfair’s skink became restricted to Round Island sometime in the mid 1800s due the invasion of rats on the mainland. In 2006 and 2007 the reptile recovery programme released 260 individuals onto Ile aux Aigrettes, and a further 500 individuals in 2010. The skinks are helping with the restoration process of the island by dispersing the seeds of endangered plants and they have contributed to the decline of invasive non-native animals, such as the Indian musk shrew, wolf snake and African land snail. Routine skink work comprises of searches and a mark and recapture programme. Soaring midday temperatures means that searches are done in the morning. I was very eager to get hands on experience so I offered to help catch some skinks! Skinks are captured by hand or using a “fishing pole” method. I never had any success with the pole but I did manage to catch one skink by hand! The trick I was told is to avoid eye contact.
Once caught, the skink is placed in a cloth bag. Back at the field station, the captured skinks were weighed, measured and their locations were recorded. As the recovery programme involves mark and recapture, we also checked each skink for identifying marks to determine if they are recaptures. As with the tortoises, every adult skink on the island is recognisable from its unique PIT tag code, however any juveniles without them are PIT tagged when captured. Recording the frequency of skink encounters is important as it allows the reptile team to estimate the survival of the population and estimate the number of skinks present.
Whilst adult skinks predate upon shrews, the shrews predate hatchling skinks and therefore have been preventing population growth of skinks on Ile aux Aigrettes. To combat the problem the reptile team set up a head-starting program: this allows juveniles that would otherwise be predated upon to reach adulthood. Pregnant skinks are captured and placed in a hatchery, where they are cared for until they have laid their eggs and are then released. The hatchlings are harvested and placed in the skink nursery where they will be grown to adulthood and released. I was able to help occasionally with the monitoring and feeding of the juvenile skinks. Supplementary food is provided daily and their diet consisted of fruit, crushed African land snail and live crickets. I fed these skinks by scatter feeding, which encourages natural foraging behaviour and provides interest and enrichment for the skinks. Another useful feeding method involved placing crickets in toilet rolls which were then placed around the enclosure.
Gunther’s gecko is the largest gecko in Mauritius and one of the largest geckos in the world. Historical records show that the gecko was once found throughout the lowland forests of Mauritius, but since the mid 1800s it has been restricted to Round Island. In 2010 the reptile team translocated 50 geckos onto Ile aux Aigrettes and the population continues to grow. Unfortunately this is not the case on the mainland, as populations are slowly declining. One of the major leading causes of this decline is thought to be the gradual degradation of forest habitats and the loss of cavity forming trees. Cavities allow geckos to take refuge, but also form important nesting sites. On Ile aux Aigrettes the reptile team have placed bamboo tubes about 1m high on trees throughout the forest. Gunther’s geckos are readily taking refuge in these tubes, and some females are using them as nesting sites. Like the skinks, Gunther work involves regular searches and mark/recapture. Again, these take place during the morning. Thanks to the bamboo tubes, it is sometimes easy to find the geckos. When under a tube, I would shine a torch into the cavity, and if I saw eggs or a gecko inside I record it. The first time I saw a Gunther’s gecko I was waiting near a tube that had eggs inside. After a few minutes my patience paid off, the female returned and I managed to get a glimpse of her before she darted into the cavity. This was a really exciting moment for me, as up until that point I had only found gecko egg shells.
The geckos are caught in the same way as the skinks, however, Gunther’s geckos cannot be PIT tagged because their skin is too fragile. Individuals are instead identified from scars, tail break marks and missing toes. I was very fortunate to learn so much about handling and morphometric techniques, as I had no reptile handling experience prior to this. Thankfully I managed not to harm the reptiles, or myself. Releasing healthy captured skinks and geckos back into the forest really is a great feeling!
Before I was due to leave Mauritius, I was delighted to be given the opportunity to work for a week and a half on Round Island. I heard so many stories about this amazing place, so I couldn’t wait to get there! Round Island is an offshore islet, situated 22.5 km off the north-east coast of Mauritius and takes about two hours to get there by boat. Its a miracle I didn’t get sick after the very choppy trip there with the Coast Guard. On approaching Round I was in awe at the sight of this mountain rising out of the middle of the ocean. When I arrived on the island what first struck me is how unspoilt and primeval a wilderness it is. After the long trek from the boat to the field station I took a well deserved rest under the shade of a bottle palm tree.
Looking all around me I could see that the island was teeming with wildlife, even more so than Ile aux Aigrettes. Telfair’s skinks are much more plentiful here, and if you didn’t watch your step you could stand on one! They are so bold that they’d climb into a hammock with me, and plop into my tea if I wasn’t looking!
Round Island restoration work has been ongoing since the late 70’s. Mammalian species such as goats, cats and rats were eradicated and dozens of endemic plants were propagated and planted. Like on Ile aux Aigrettes, tortoises were translocated to tackle the problem of invasive plants and help with the regeneration of native ones.
Most of my time on Round Island was spent working on the tortoise survey. Round has two species of tortoise, the Aldabra giant tortoise and the Radiated tortoise from Madagascar. As well as undertaking the survey, I also did tortoise searches. This was to see how far they have spread over the island and their general condition too. On my first morning I rose at 5am, to begin searching at 6am. The tortoises are usually on the summit in the morning, and we have to work as quickly as possible as temperatures can reach a scorching 30ºC by midday! Once we reached the summit the tortoise hunt began! Unlike on Ile aux Aigrettes, none of the tortoises are sexually mature, though both species vary in age and size. Despite their size they can hide in incredibly small spaces but their tracks led us to any that were hiding, usually under the shade of a large palm! Once I managed to lure a tortoise out of its slumber, one of the team had the task of lifting the tortoise onto the scale to be weighed. Weights vary from 10kg (a young Radiated tortoise) to 100kg (an older Aldabran)! Once weighed, morphometric measurements were taken and then they were released.
Round has one species of endemic snake, the Keel-scaled boa. It is a medium size snake with a total length of approx. 110 cm, it is also the island’s top predator. Searches for the boa are done at night and after days of hard work under the blistering sun it was a welcome change! Searches took about 2 hours, and involved walking along transect lines and recording species observed. Data such as time, duration of survey, temperature, wind strength, cloud cover, moon phase, amount of shade and rain etc was also recorded. I saw lots of Gunther’s gecko, Durrel’s Night gecko and the Ornate Day gecko but unfortunately no Keel-scaled Boa! After my last night survey, we had just arrived back to the field station when a juvenile boa dropped down from the kitchen ceiling! Unfortunately it slithered away before we could capture it, but I was glad to catch a glimpse of this beautiful snake.
Before volunteering in Mauritius I only had experience in working with captive-reared animals. I feel very privileged to have had the opportunity to work with these endangered and charismatic species, which the reptile recovery programme allowed me to do. The conservation efforts have evolved from translocations, captive breeding and intensive monitoring, to addressing the causes of their decline, through invasive species control, habitat protection and ecosystem restoration. It is inspiring to think that if it wasn’t for the efforts of MWF and its dedicated staff these species could have been lost forever.
About the Author: “Maeve is a zoologist specialising in behavioural and evolutionary ecology in birds, with particular emphasis on endangered species. You can find her on Linkedin