Tag: nature

Volunteering with ‘Data 4 Nature’ – Wandering the Woodlands

By now, I’m sure you’ll know that I’ve been trekking around Sheffield’s nature reserves, collecting data for the National Lottery Heritage funded ‘Data 4 Nature’ project. The third and final set of surveys I carried out with ‘Data 4 Nature’ involved monitoring the condition of Sheffield’s woodland reserves. The Sheffield and Rotherham Wildlife Trust take care of some of the most beautiful woodlands in the area, including Wyming Brook: my favourite place to go take a breather from the stresses of university life. We are lucky to live in such a green city, and being 10.4% woodland by area, Sheffield is actually the most wooded city in Britain. We all know the benefits woodlands provide for our physical and mental health: they clean the air we breathe, give us space to exercise our bodies and reduce mental fatigue. We’re not the only ones to benefit though; woodlands are home to more wildlife than any other landscape. Take the humble oak tree – it supports birds nesting in its canopy, small mammals burrowing in its root system, bats roosting in its trunk and up to 280 different insect species living amongst its branches. We need to protect woodlands to make sure they continue to give wildlife a home. So, ‘Data 4 Nature’ has created a monitoring protocol to assess the condition of four key woodlands in Sheffield: Blacka Moor, Moss Valley, Fox Hagg, Wyming Brook. If we know the current state of our woodlands, management can be tailored to maximise benefits to wildlife in the future.

How do we define woodland condition?

‘Data 4 Nature’ developed a protocol for defining the condition of a woodland based on national standards. Woodland condition is broken down into two elements: structural attributes of the woodland, and species composition of the trees. When we talk about woodland structure, we are thinking about things like the amount of dead wood, how many glades are present, and how many invasive species there are in the area. Species composition considers which tree species are found in the woodland, as well as their diversity and age.

The woodland condition surveys started right back in autumn 2018. The team decided to do the surveys twice round, once in the winter, and once in the summer. The winter surveys focused on the structural aspects of woodland condition. We had to wait until the summer to look at species composition – it’s incredibly hard to ID tree species with no leaves! Luckily, the ‘Data 4 Nature’ team don’t expect us to be that good at species ID.

Winter condition training took place in all weather conditions! (Photo credit: Julie Riley)

Our method:

Each woodland reserve was divided up into 1-hectare grid cells, measuring 100m2. In teams of three or four, volunteers followed a pre-planned route through the grid cells, taking measurements as we went. These routes didn’t always stick to the footpaths, so we had to scramble up and down the valley edges to stick as closely to our route as possible (I only fell over once, surprisingly). The biggest challenge we faced was not getting lost in the middle of the woods! So, what were we looking for as we orientated our way between brambles and through thickets?

Evidence of browsing –

Browsing by woodland mammals can severely damage woodland biomass. We assessed how much vegetation in each survey plot was damaged by deer and squirrel browsing, to see how much it impacts the ecosystem. The deer population is currently growing at Blacka Moor Reserve – notable by the number of droppings we found across the landscape! – so it is especially important to ensure deer are not stripping away too much of the woodland. We saw a herd of deer tracking though Blacka Moor during our survey. I’ve never seen deer out in the daylight before, so this was a rare and special sighting.

Invasive species –

We identified and estimated the percentage cover of invasive plant species within each grid cell. In the winter, the most common invasive species you will see are rhododendron and cherry laurel. These species are evergreens, thankfully making them easy to identify in the winter months.

Rhododendron can be identified by its dark glossy leaves, elliptical in shape and measuring around 22cm. These leaves grow in a whorl around a hard, light brown stem. The species has attractive pink to purple flowers located in the middle of the terminal whorl of each branch. Rhododendron is believed to have been introduced to the UK from Gibraltar in 1763. By 1893, it was being sold on London markets as a flowering pot plant. Rhododendron is incredibly difficult to eradicate from landscapes; its small seeds disperses rapidly via the wind and it can grow to fill any space available to it, either remaining as a small shrub, or growing to outcompete native vegetation. Mechanical methods of removing it are highly costly. It was estimated that £30 million would be needed to clear the species from the Snowdonia National Park alone.

Cherry laurel is another invasive species which is easily confused with rhododendron. It also has leathery, dark green, oblong leaves, but these are duller and smaller than rhododendron leaves. Cherry laurel also has erect racemes of white flowers that give rise to black cherry-like fruits. The species was planted in the UK in the 17th Century and was often used for hedging and game cover. Its abundant fruit makes it easy to disperse via birds. Cherry laurel casts a dense shade that excludes other species from accessing light resources. This means it can dominate the shrub layer and reduce diversity in the ecosystem.

Estimating how well established these two species are in Sheffield reserves will allow the Trust to develop management strategies that best prevent it from hindering the growth of native vegetation.

Woodland edge –

Transitions zones between one habitat and another are called ecotones. Ecotones are most valuable to wildlife if change is gradual between neighbouring habitats. For example, an edge which transitions from woodland, to shrub, to grassland is better at allowing wildlife to move through it than woodland which abruptly turns to grassland. We looked at whether the woodland edge measured at least 1.5 times the height of the nearest mature trees, to see if there is a wide edge between the woodland and neighbouring habitat in our woodland reserves.

Temporary open space –

The Wildlife Trust need to know how much temporary open space is present in the woodland reserves. These are areas in which trees could regenerate if we stopped cutting back vegetation and allowed natural ecological succession to play out. Areas where trees could regenerate include glades, rides, footpaths and areas of clear-felling. These areas had to be at least 10m in diameter and have less than 20% shrub/tree cover to be counted in our surveys.

Glades and rides are also valuable because they replicate woodland edge habitat inside wooded areas. This creates a ‘heterogenous’ habitat: a habitat with lots of different microhabitats within it. For example, a heterogenous woodland may have some closed canopy areas, open canopy areas, scrubby areas, grassy areas, wetland areas and more. This means a whole host of wildlife adapted to these different microhabitats can be supported. Having ecotones both between habitat types and within woodland is highly valuable because of the range of wildlife they let thrive. Ecotones are more valuable than many other woodland habitats, excluding veteran trees.

Wetland features –

This one was easy – we simply recorded the presence of any pools, ponds, rivers, brooks, streams or bogs in our grid cells. The Trust are aiming to have no net loss of wetland areas in their reserves, as wetland features provide a crucial microhabitat for aquatic wildlife.

Presence of dead wood –

Identifying how much dead wood was present in each grid cell was important for the Trust to assess how suitable woodland areas are for Willow Tit populations: one of the fastest declining bird species in the UK. Willow Tits require open woodlands with scrubby areas and plenty of dead wood. The Trust have been working to increase the Willow Tit population in Fox Hagg over the past four to five years by providing more suitable habitat.

Species composition –

Once the days had started to draw out and the new spring leaves had burst-bud, we could assess the species composition aspect of woodland structure. We used ID sheets provided by the Trust to help us identify and record the presence of tree species in the woodland. There are 16 native and 7 non-native species that are common in the Sheffield area, which we encountered most regularly. We also put the trees into age classes based on the diameter of the tree at breast height. These age classes were: sapling, young, mature and very mature.

Results:

Overall, our surveys showed that the woodland reserves are in good condition. The results indicated that regeneration of native species is ongoing and species diversity was high across all sites. The Trust plan to use this data as a baseline to highlight any future changes in species diversity and composition in the woodland reserves.

Percentage cover of different species making up the canopy cover in each reserve (Figure credit: Patricia Malcolm).

The Fox Hagg surveys showed that there is plenty of dead wood in the woodland to support a viable Willow Tit population. This is great news for the Land Management Team at Fox Hagg, who have been working to clear out glades for the species. However, Fox Hagg represents a difficulty that woodland managers often face: managing to benefit one particular species, versus managing the site as a whole. Normally, woodland managers would aim to have open space within 10-40% of grid cells. At Fox Hagg, open space is now found in 70% of grid cells to benefit the Williow Tit. This will make it less suitable for woodland inhabitants that prefer a closed canopy structure.

Map of Fox Hagg showing grid cells with dead wood present. The majority of the reserve has dead wood present, making it suitable to support a Willow Tit population (Figure credit: Patricia Malcolm).
Map of Fox Hagg showing grid cells with open space. The majority of the reserve is open woodland, making it suitable to support a Willow Tit population (Figure credit: Patricia Malcolm).

Wyming Brook, on the other hand, is an important habitat for the Wood Warbler: a species that prefers closed canopy mature woodland. Wyming Brook was found to only have open space in 40% of grid cells, showing it has been well-managed to support the Wood Warbler. Crucially, the data showed that grid cells without open space correlate with areas the Wood Warbler is known to occupy. This shows how the Trust can use the data to tailor management to each site specifically.

A map of Wyming Brook showing grid cells with open space present. The majority of the woodland is closed canopy, making it suitable to support a Wood Warbler population (Figure credit: Patricia Malcolm).

“The volunteers have done a fantastic job to collect and collate this monitoring data for Fox Hagg & Wyming Brook and it is very much appreciated. The data gives us a fantastic baseline to work with and it is great to see that we are meeting our targets for specific woodland condition attributes such as the presence of dead wood and temporary open space in the correct areas for our star species such as willow tit and wood warbler. The results will also help us identify areas where we can improve and target our management to help improve habitats for wildlife across these two fantastic nature reserves in the Rivelin Valley.”

Rob Miller, Reserve Manager

Volunteers spent over 500 hours rambling through Sheffield woodland to complete these surveys, so it’s great to see that the data we collected has already been used to improve management of woodland reserves. As always, I really enjoyed taking part in the woodland condition monitoring. It was a great opportunity to brush up on my tree species ID skills (crucial when you study ecology!), while exploring these beautiful woodlands. Get in touch with your local Wildlife Trust to find out how you can help protect wildlife in your area. Treat your mind and body to the benefits of being in woodland, whilst giving something back to the wildlife in your local area – what could be better?

Volunteering with ‘Data for Nature’ – an opportunity ‘newt’ to be missed

Hello again! This post is all about another of my volunteering adventures with the Sheffield and Rotherham Wildlife Trust. If you read my last blog post, you’ll know I’ve been working with the National Lottery Heritage funded ‘Data for Nature’ project, which aims to improve ecological data bases for nature reserves in and around Sheffield. If you didn’t suss it from the cheesy pun in the title, my latest excursions had me on the hunt for newts. Specifically, the elusive Great Crested Newt. Over a three-month period, a handful of volunteers completed six Great Crested Newt surveys in Sheffield’s Woodhouse Washlands nature reserve. Our aims were: a) to estimate the population size of Great Crested Newts in the area, and b) to work out how suitable this site was as a newt habitat. This will help the Wildlife Trust improve and maintain the reserve so the newt population can thrive both now and in the future. Like all the ‘Data for Nature’ initiatives, these surveys help improve databases held for wild populations in the Sheffield and Rotherham area and allow the Trust to improve management of its reserves to best suit wildlife living there.

Great Crested what?

So, what actually is a newt? Newts are salamanders, which are a group of amphibians characterised by their lizard-like appearance. They have slender bodies, rounded snouts, short limbs and a tail. Unlike other members of the salamander family, newts are semi-aquatic. This means they live in both terrestrial and aquatic habitats. The Great Crested Newt is a species of newt that only lives in Europe. Females can reach 7 inches in length, making them the largest species of newt on the continent. Thanks to its prehistoric demeanour, the Great Crested Newt is often described as a mini dinosaur. They are near black in colour with bright orange bellies and spotted flanks. The males especially, with their warty skin and crinkly crest, do look like small, slightly pathetic Stegosauruses. These warts are actually vital to the newts’ survival, as they secrete a milky rancid substance that dissuades predators. The species breeds in ponds in the spring before moving into woodlands, grasslands and hedgerows to feed on invertebrates later on in the year. We carried out our surveys in the late spring when the newts are in their aquatic breeding habitat. This made it easier to locate and count the newts. When you imagine trying to find newts in a woodland the old ‘needle in a haystack’ image comes to mind.

Getting up close and personal to a Great Crested Newt. Here, you can see the warty skin and spotted flanks that characterise a Great Crested Newt. Its crest is flaccid because it is out of the water. (Photo credit: Libby Pool).

Other newt species…

We recorded sightings of other newt species living in Woodhouse Washlands, such as the Smooth Newt and the Palmate Newt, though we didn’t come across many of the latter. We counted these other species of newt to see how well a variety of species are doing in the area. The Smooth Newt, also aptly known as the ‘Common’ Newt, is the species you will most likely see in your own garden or pond. They are grey-brown in colour with an orange belly and neat spots all over. Confusingly, male common newts also develop a crest during the breeding season. You can use this crest as a neat way of telling a Great Crested Newt and a Smooth Newt apart: the Smooth Newt’s crest runs unbroken for the entire length of its body and tail, while the Great Crested Newt has a break in its crest where the tail and body join.

This photo shows the difference between the underbellies of a Smooth Newt (left) and a Great Crested Newt (right). You can also see that the Great Crested Newt is black in colour, while the Smooth Newt is grey. (Photo credit: Libby Pool).

Our survey design

The Great Crested Newt is actually listed as a European Protected Species. This means that the newts, their eggs and their breeding sites are all protected by law and it is an offence to disturb them. This law dictates that a licensed ecologist must be present for any survey carried out on Great Crested Newts. To fulfil this requirement, we volunteers worked with license holders from Wildscapes CIC: an environmental consultancy and subsidiary of the Sheffield & Rotherham Wildlife Trust. Only 2-4 volunteers helped per survey to minimise disturbance to the newts on site.

To carry out an accurate newt survey, license holders are required to collect population data in three different ways. Our three methods were: bottle trapping, torching and egg searching. Bottle trapping involves counting the number of newts caught in bottle traps set up in the ponds. As the name suggests, these ‘bottle’ traps are not the most high-tech ecological equipment…they are literally 2 litre bottles with the nozzle cut off and inverted. Crucially, however, they allow newts to swim in to the bottles but prevent them from swimming out again. We set these traps up around the perimeters of all 6 ponds on site at dusk. As newts are nocturnal, we had to wait until morning to see how many we’d caught. Once the traps were set, we waited (often at the pub) until sunset to complete our second method of data collection: counting the number of newts in each pond by torchlight. Using a powerful torch beam, we skimmed the bottoms of the ponds for any signs of newt activity. We didn’t get home until around midnight after this torchlight search, only to be up at the crack of dawn the next day to release our trapped newts (who needs sleep, right?). The plastic bottle traps get hot very quickly if left in the sun too long, so we had to make sure we had counted and released any trapped newts before the morning sun cooked them. Much to our delight, we found handfuls of newts in our bottle traps on those early mornings. As my friend and fellow volunteer Beth said, “at least we didn’t get up at 5am for newt.”

An example of the handfuls of newts we released from our bottle traps at dusk on the second day of surveying (Photo credit: Libby Pool).
A male Great Crested Newt in a bottle trap with its namesake crest on show (Photo credit: Libby Pool).

Our final method of data collection was to record the presence or absence of newt eggs at each pond. Newts lay their eggs on leaves around the edges of ponds. Once deposited, they nimbly fold the leaf in half to protect the tiny egg inside. Check out this fascinating photo I took of a newt embryo developing in its egg we found on site!

A newt embryo developing on a leaf found on site (Photo credit: Libby Pool).

To assess how suitable each pond is as a Great Crested Newt habitat, volunteers completed a Habitat Suitability Index (HSI) during one of the surveys. This is a standardised method in which different aspects of pond suitability are analysed, including: pond area (m2), presence of fish and percentage macrophyte (vegetation) cover. This final aspect of the survey allowed the Trust to work out how suitable Woodhouse Washlands is as a newt habitat, so they could adapt their management of the site to maximise its ability to support a growing Great Crested Newt population in the future.

And finally…the results!

Overall, the volunteer team found some really positive results. We estimate that the population of Great Crested Newts in the Woodhouse Washlands reserve is 82 individuals – this is a really promising number! Six of the ponds on site scored ‘excellent’ in our HIS survey too. This shows us that a good number of ponds on site are already highly suitable habitats for the newts. This also highlights the ponds that scored lower in the HIS survey, so management can work to improve these areas. Interestingly, a correlation was found between the number of Great Crested Newts found in each pond and the HSI score. This means that ponds with higher HIS scores typically housed more newts. One pond on site was nicknamed ‘the party pond’ by volunteers; every time we emptied the bottle traps from this pond, we had caught a huge number of newts (see the photo above!) This pond turned out to be on of those that scored ‘excellent’ in the HSI survey, so it is no wonder all the newts wanted to be there to join in the party.

This graph shows the correlation between the mean number of newts found in each pond compared to the HSI score. (Figure credit: Isabel Commerford).

A volunteering oppurtunity ‘newt’ to be missed…

The newt surveys were by far the most enjoyable of the surveys I’ve been involved with for ‘Data for Nature’ so far. Despite the sleep deprivation, it was actually really good fun being out with a group of welly-booted people stood around ponds at midnight – we had a lot of laughs. It was really nice to be out in nature at dawn and dusk: the times we don’t normally get to appreciate it. Watching the sun set over the reserve was stunning, and one of the team had the good idea of bringing a bat detector so we could listen to the bats overhead in the trees. One evening, we even saw a fox patrolling the landscape. Its experiences like these that make volunteering with the Wildlife Trust so special, so get onto your local Trust’s website and find some opportunities near you.  

  • Releasing the newts from our bottle traps at dawn (Photo credit: Oskar Seime).
  • “At least we didn’t get up at 5am for newt” – Beth Lightburn. (Photo credit: Oskar Seime).

You can learn more about ‘Data for Nature’ and volunteering here: https://www.wildsheffield.com/wildlife/wildlife-conservation/data-for-nature/

Check out these web pages for more information on Great Crested Newts:

If you’re interested in learning more about the other species of newt we surveyed, you can find out more here:

Find out more about Woodhouse Washlands here: https://www.wildsheffield.com/reserves/woodhouse-washlands/

Volunteering with ‘Data for Nature’ – Hunting for Harvest Mice

Since autumn last year, volunteers have been scouting nature reserves around Sheffield and Rotherham for everything from newt eggs, to skylarks, to harvest mouse nests, and much more in between. I am one of these eager volunteers, working under the Wildlife Trust’s ‘Data for Nature’ initiative. Over my next series of blog posts, I want to share with you why getting involved with ‘Data for Nature’ was one of the best decisions I made during my time at university. Volunteering for your local Wildlife Trust is not only a vital way of helping protect wildlife in your local area, it’s also great fun to get involved with!

I initially signed up to volunteer with the Wildlife Trust because I wanted experience in ecological surveys. However, my volunteering has become more than something to write on my CV. I’ve met so many like-minded people and learnt so much more about nature. You essentially get to go walking in nature reserves, collecting valuable ecological data on the way. But, before I go off on a spiel about how great volunteering is, I should tell you what ‘Data for Nature’ actually is and why it’s a worthwhile cause to devote your time to.

What is ‘Data for Nature’ all about?

‘Data for Nature,’ funded by the National Lottery Heritage Fund, was born in response to the Sheffield State of Nature report, which stated that gaps in the city’s ecological records should be addressed. The Trust aims to improve its database of wildlife populations within Sheffield and Rotherham. To do this, the Trust has set up rigid methods of monitoring for each species and/or habitat type. These robust monitoring frameworks are taught to volunteers on training days, so they know how to carry out each specific survey type. Armed with the ‘know-how’ to complete surveys on our own, us volunteers go out en-mass to other reserves and repeat the process. All in all, this massively increases the Trust’s capacity to collect data. In the words of Julie Riley from the ‘Data for Nature’ team:

“we are developing set methodologies so that surveys can be repeated and analysed over the long term, helping the Trust to see how effective its management of each reserve is, and make changes if needed.”

The first survey….harvest mice populations

The first ‘Data for Nature’ survey began in November last year, when we searched the Carr House Meadows reserve for harvest mouse nests. In case you’ve never seen one, the harvest mouse is the smallest rodent native to Europe. Adult harvest mice can weigh as little as a 2p piece! You’ll find harvest mice from central Yorkshire southwards, scurrying in long grasses and reeds. The harvest mouse is the only British mammal to have a prehensile tail, which it uses as a fifth limb to hold on to the grass stems it feeds and breeds in. In the breeding season, harvest mice weave dome-shaped nests out of grass. These are found between half a metre and a metre above-ground in dense vegetation, out of sight of predators stalking the grounds below.

One of the volunteers with a harvest mouse nest found at Carr House Meadows! (Photo credit: Sharron Burton)
A harvest mouse nest next to a 20 pence piece for size comparison (Photo credit: Nick Howard)

In this survey, we systematically searched for nests as an indicator of harvest mouse presence. Searching for mice themselves would be too time consuming and, unlike mice, nests don’t move, so you have a much higher chance of finding them! The Carr House Meadows reserve is divided up into a series of fields. We searched the perimeter of each field, where the vegetation is taller and denser. We moved around the perimeter taking quadrats of a given area. Within each quadrat, we measured:

  • Whether or not 50% of the vegetation was over 0.5 metres tall.
  • How well connected the area was.
  • The dominant plant species in the area.
  • The presence of any harvest mouse nests.

Why did we measure these things?

These aspects of the reserve were measured to assess how suitable it is as a breeding habitat for harvest mice. For example, the minimum height a harvest mouse likes to build its nest above ground is around 0.5 metres, so assessing whether of not more than 50% of the vegetation is at least this height allows us to see whether there is substantial tall grass available for the mice to nest in. A suitable breeding habitat would also be well connected to foraging grounds by dense grasses or shrub margins. This allows mice to move between their nest and foraging sites through dense grasses, which best obscures them from predators. We also identified the dominant plant species in the area to see which vegetation best supported nesting. In our training session, we were shown how to identify common grasses and shrubs in the reserve. We were also taught how to identify harvest mouse nests as some bird species, like reed warblers, construct similar looking spherical nests. This training was very useful when we did come across nests which turned out to belong to birds rather than harvest mice. When we found a suspected harvest mouse nest, photos were taken and sent to a mammal expert at the Trust who confirmed the nest’s identity.

Surveying the dense vegetation in the perimeters of the fields at Carr House Meadows (Photo credit: Pete Tomlin)

The results…

We were excited to find two nests at Carr House Meadows. Though two doesn’t sound that impressive, this gives us great hope that the reserve does serve as a suitable breeding habitat for harvest mice. These maps, produced by Hannah Davis, show the locations of these two nests. The first map shows the results for our vegetation cover analysis. This indicates that 50% of the vegetation cover in the quadrats neighbouring the nests was not greater than 0.5 metres. This is surprising, considering the typical nesting habits of harvest mice. The second map shows the results for the overall connectivity of the quadrats neighbouring the nests. Both nests seem relatively well connected, particularly the nest in location one. This initial analysis suggests that connectivity may be more important to a harvest mouse choosing a nesting site than vegetation cover. Pete Tomlin from the ‘Data for Nature’ team suggested we may only have found two nests in the reserve because there is not enough rough grass cover around the field edges to allow easy movement. This makes sense, as harvest mice need nesting sites to be well connected to their feeding grounds by dense grasses, allowing predator evasion during foraging. Increasing the rough grass cover around the reserve perimeter may be crucial in encouraging population growth. The final map shows the results for the dominant plant species around the nest. Our two nests seem to have a lot of bramble in neighbouring quadrats, suggesting this is a good plant species for the nests to be hidden within.

The results for vegetation cover analysis as part of the harvest mouse survey at Carr House Meadows
The results for the connectivity analysis as part of the harvest mouse survey at Carr House Meadows
The results for the dominant plant species analysis as part of the harvest mouse survey at Carr House Meadows

Since the survey at Carr House Meadows, ‘Data for Nature,’ volunteers have tried out the protocol at another reserve: Woodhouse Washlands. A full survey is due to take place this autumn. It will be interesting to see if results seen at this second site are similar to the results above. Importantly, these results will give the Trust the opportunity to make changes to the way these reserves are managed. This should involve increasing connectivity, so more harvest mice use the site to breed in the future.

Scavenging the hedgerows for harvest mouse nests in this first survey for ‘Data for Nature’ made me eager to get out and do more. If, like me, you enjoy digging around in hedgerows, ponds and woodlands, sign up to volunteer with your local Wildlife Trust.

You can learn more about ‘Data for Nature’ and volunteering here: https://www.wildsheffield.com/wildlife/wildlife-conservation/data-for-nature/

Check out this page for more information on harvest mouse ecology: https://www.wildlifetrusts.org/wildlife-explorer/mammals/harvest-mouse

Find out more about Carr House Meadows here: https://www.wildsheffield.com/reserves/carr-house-meadows/

A World Without Sex?

There are many weird and wonderful curiosities in nature. One such oddity is that some animals are able to create offspring without ever having sexually reproduced. How on earth is this possible? If females can go at it alone when producing offspring, will we one day be seeing a natural world without sex? If you’re interested, read on…

Zookeepers at Louisville zoo, USA, were astounded when they found Thelma the python had laid 61 eggs in her enclosure. But why were they so amazed? Laying eggs is quite normal for pythons. What made this event so miraculous was that no male had ever been anywhere near Thelma. How did she produce offspring without an act of copulation?

Thelma had become the first reticulated python in the world to have a ‘virgin birth,’ triggering new genetic research into this peculiar phenomenon. DNA evidence confirmed that Thelma really was the sole parent of the hatchlings. In the words of Bill McMahan, the zoo’s curator of ectotherms, “I guess sometimes truth is stranger than fiction.”

Despite this, such ‘virgin births’ where females produce offspring from an ovum without fertilisation are actually seen throughout nature. Scientifically termed ‘parthenogenesis,’ virgin births have been recorded in species from bees to Komodo dragons and new cases are being recorded all the time. But how can it be possible to fertilise an ovum without a sperm?

The nuts and bolts…

Parthenogenesis may occur in two ways, which you can read about here. In the case of Thelma, she replaced the fertilising sperm with a ‘polar body:’ a by-product of her dividing cells. All offspring are half clones of their mother.

Other examples of parthenogenesis in nature…

Two particularly interesting examples of parthenogenesis occur in species of stick insect and sawfish. Many scientists have predicted that females turn to parthenogenesis as a last resort. When population sizes are low, it becomes less likely that a female will find a mate. This is especially troublesome for shark species that lead solitary lifestyles, roaming open ocean waters and only occasionally bumping into others. One species, the smalltooth sawfish, was found to commit parthenogenesis in the wild in 2015. This discovery came completely by chance. Ecologists studying genetic variation in the population came across young, healthy sawfish created through virgin births. This was quite the revelation! The species is likely using parthenogenesis as a survival strategy against their declining populations. As ecologist, Kevin Feldheim, described, “if they can’t find a mate, it’s possible this mechanism kicks in as a last-ditch effort for these females to pass on their genes.”

Despite this, female stick insects actually choose to go solo in reproduction even when presented with ample mating opportunities. Reproduction can be costly for females, so they’d rather go at it alone. In studies, female giant prickly stick insects have fought off advancing males by kicking their hind legs. They also produced anti-aphrodisiac chemicals to put the boys off.

Female giant prickly stick insects will curl up their abdomen like this one is and kick their hind legs to ward off lustful males. (Photo from Wikipedia Commons).

Do we really need males?

These virgin births beg the question: what does the future hold for males? Male giant prickly stick insects could be at risk of dying out, as females will quite happily reproduce via parthenogenesis, only produce female offspring when they do so. However, in many species including stick insects, evidence suggests males will force females to mate with them. Typically, males win these sexual conflicts more often than females do, giving them a fighting chance at survival. This is thought to be one of the reasons why parthenogenesis remains rare. Another reason is that it typically requires optimal conditions to occur. Thelma, for instance, was kept at perfect temperature with an unlimited food source. She had “the optimal conditions to make the biological leap into solo parenthood” claimed McMahan. Obviously, such perfect conditions rarely occur naturally.

Parthenogenesis does have its advantages. For example, if a species became isolated on an island, it would be able to increase its numbers without the need for sexual reproduction. This has been seen in species of whiptail lizard. However, virgin births can carry huge costs for the offspring they produce. Parthenogenesis is essentially inbreeding, leaving individuals vulnerable to diseases and malformations associated with decreased genetic diversity. For this reason, scientists recommended that Komodo dragons were not kept in captive isolation for fear they may begin cloning themselves. This would reduce genetic diversity in the already vulnerable population. Similarly, a captive pit viper gave birth to one stillborn snake and four undeveloped ova through parthenogenesis. This indicates that ‘virgin births’ are far from ideal and often end in early mortality or maldevelopment.

For now, it seems the boys are safe. Species do require males to maintain viable populations as the health costs of decreased genetic diversity are just too great. Evolution is a clever phenomenon. It has given species a way to reproduce asexually when the chances of mating sexually are dire. This helps populations persist through times of stress. However, it has created mechanisms to control virgin births, preventing them from becoming so common that species suffer from inbreeding depression. Thanks to evolution, we won’t see a world without sex anytime soon.

Caught your interest? Read more at:

http://www.bbc.co.uk/earth/story/20141219-spectacular-real-virgin-births

http://www.bbc.co.uk/earth/story/20151216-virgin-births-are-happening-everywhere

https://news.nationalgeographic.com/news/2014/10/141023-virgin-birth-pythons-snakes-animals-science/

An Introduction…

A little bit excited about ecology?

I’m Libby, an Ecology and Conservation student at the University of Sheffield. I’m starting ‘Bees, Trees & Curiosities’ as a means of sharing my thoughts and findings on anything to do with nature and the environment. There are so many wonderful, curious things in the natural world. This will be my way of celebrating them. I’ll write about the ecology of species I particularly like, explore wider environmental issues and maybe even go a bit ‘travel blog-esque’ in talking about my walks and travels. I have a great fondness for bees and happen to be starting a beekeeping training course tonight – so posts about bees can only be expected! I hope this sounds like something someone, somewhere, might like to read.

We all need to be a little more considerate of the natural world in this day and age. I hope my ramblings show you that nature deserves to be talked about. If you have any suggestions of things you would like me to research and write about, please do get in contact. For now, here’s a photo of my doing what I do best…surveying!