Technology and Identification

 In today post I want to illustrate how a variety of techniques is somewhat needed to verify the presence of a species on a site. My case study for this is the Harvest Mouse. Harvest Mice are the UKs smallest rodent weighing only 6g when adult and not a species I expected to find on my land.

The habitat is suitable, thick brambles and stands of tall grasses and reeds are separated from agricultural land by a hedgerow. When I first started to manage my patch, I did wonder if Harvest Mice occupied the site and put out some cut of tennis balls to see if any would nest in them, this was a complete failure a) because even with GPS recording them, I lost them in the dense vegetation and b) because the frequent winter floods swept them away. I saw no signs of their presence although I have looked for nests and whilst I have seen bundles of grass, they were never distinct enough for me to rest an identification on.  

I assumed Harvest Mice if present were restricted to the field which predominantly grew wheat and corn, that was until this year.

I blogged earlier in the year about my purchase of a static batlogger and my success with it. From June I have been putting it out to record the bat species. I am still getting a handle on interpreting that data and in my June post I explained that I had detected Harvest Mouse calls.

Harvest Mice are known to vocalise in ultrasonic pulses between 20 and 70 kHz, with four notable call types that are distinct from other rodents. The data I collect with the Batlogger is analysed through the BTO pipeline. This outputs the results of all recorded sounds with an assigned identification, this identification is qualified by a probability that the sound file matches the sonograms known for that species. It is generally that any probability lower than 0.5 is discarded. This value seems very low to me, and I had decided only to accept probabilities above 0.75 and 0.9. The spread of the data can be seen in the boxplots below.

Total

As you can see the average probability is around 0.6 and the number of identified files is very low. For this reason and the thinking that the detectors’ location did not ideally line up with suitable habitat I decided to not count Harvest Mice as a resident species at present but to keep an eye, or rather, sensor out.

Given their tiny size it is very difficult to see a Harvest Mouse in the wild, specific surveys needed to be conducted. I doubted that my three trail cameras would yield much given their locations and the fact that I have always considered Harvest Mice to be a species that doesn’t come down to the ground much and spends much of its time in the vegetation.

I was proved wrong on the 19^th August. A single image and 10 second clip from my Mostela camera revealed what seemed to be a harvest mouse.

The individual in shot was tiny, its tail thick, its ears small and its nose blunter, but the image was black and white, and I wanted data to back up my gut. I posted the image to the Mammal Society Facebook group to garner opinions and set about researching. My Mostela is regularly visited by Wood Mice and shrews, and this individual had none of the ‘vibe’ of those species. As you can see from the images below the mouse was about 2.265 inches long (Head and body length) this equates to 57mm right at the lower end of the expected range of Harvest Mice and well below that of the Wood Mouse. 

In the image below I show a Wood Mouse so that you can see the size difference.

Research indicates that Harvest Mice do travel along the ground. At this time of the year, they should be breeding and be using breeding nests in dense reeds, grasses, brambles or cereals. The field by the mostelas was sown with wheat which due to the hot weather and the variety grew little higher than 40cm and was harvested on the 5^th July. Maybe the nest was destroyed then and the mice dispersed into my patch.

What I like about this story is the way in which the technology and research work in tandem to identify a hitherto unconfirmed species. This identification used two remote recording devices, a host of Mammal experts on Facebook, and deep dives into two books (Sound Identification of Terrestrial Mammals of Britain and Ireland, and Mammals of the British Isles)

It gives me a new drive to investigate this species to establish if they are a resident under reported species. I will continue to use the Batlogger relocating it closer to the mostelas and conducting a proper winter survey looking for old nests. I ll report back here as and when I find out more.

Derek Gow the Radical?

By happenstance I stumbled upon the Radio 4 program ‘Radical’ this week. It is not a show that I have been aware of in the past, but this week’s subject piqued my interest. ‘Radical’ is a twice weekly BBC radio (Sounds) podcast which highlights "pioneering thinkers, bold innovators and influential voices". The episode that caught my attention was an interview with Derek Gow. Many in the nature conservation world will know of this pioneer of rewilding but for those that don't here is a quick recap. Derek Gow is a UK farmer currently living in Devon, where he has diversified from traditional farming to become a reintroduction expert. He has been a significant player in the reintroduction of Beaver, Water Vole and White Stork back to the UK. He has written several books and is currently rewilding his 300-acre farm.

What makes Gow’s argument so compelling is not simply that rewilding works, but that it exposes a national contradiction, Britain loves the idea of nature while often resisting the practical disruption needed to restore it. That tension sits at the heart of the debate around beavers, reintroductions and landscape-scale recovery.

I first came across Derek when I was researching Water Voles and trying to establish possible habitat suitability values in the local area, but he is perhaps best known for his work on the reintroduction of Beavers. His appearance on ‘Radical’ was a thoughtful interview of Derek's goals, successes and failures. Most interesting was his critique of the bureaucracy inherent to the politics of modern nature conservation. His frustration at the roadblocks that are put in his way are palpable and I have some sympathy with him. I have a dream of rewilding part of my tiny patch or at least do same habitat creation, but the number of permits and permissions needed not to say anything of the money required can be disheartening. Derek however has been very successful and has some very clear goals and ideas in mind.

The discussion in the podcast was wide ranging, and I encourage anyone interested to take a listen. The interviewer, obviously a non-specialist asked pertinent question and had done their homework. Derek quite succinctly describes the nature depleted landscape in which we inhabit today and explained some of the reasons. In essence it all boils down to two seismic shifts in human evolution, the agrarian revolution 10000 BCE and the Industrial revolution of the 18th and 19ᵗʰ Centuries. Both events substantially changed the way in which humans lived, affording them greater survivability and secondly the ability to enjoy down time to follow pursuits outside of just survival, the side effect of this was an immense impact on the flora and fauna of the planet.

When looking at such epic scales, it is worth remembering that we are still so close to the Industrial Revolution that we cannot yet see the wood for the trees, pardon the pun. Ecosystems are still responding to changes that took place very recently in evolutionary terms, and in many places, they are being denied the space and time needed to settle into any new dynamic equilibrium. Perhaps it is our short life spans that make the current situation feel uniquely terminal. Or perhaps the real problem is not that nature cannot recover, but that the scale and speed of the changes we have imposed have made recovery far harder than it needs to be.

It is interesting to note that on a global history scale nature will be okay, it will be different but barring the total annihilation of the planet life will find a way. Do not forget we are part of nature and it us, 55% of our bodies cellular mass is composed of bacterial cells, many living in symbiosis with us. We can trace our lineage back to the same cells or protocells that created every organism on the planet. However, trusting to the norms of galactic time in our short lives is not very human. So, I will move away from the grand philosophy to the examine the smaller scale of nature conservation.

The first point to explore is the contradiction in Britain today. Britain is unusual in the strength of its public affection for the outdoors, national parks, Sunday walks, public footpaths and large conservation memberships are all part of the national self-image. The RSPB alone has around 1.2 million members and the Wildlife Trusts around 940,000. With so much public interest, why are we still so nature depleted? The 2023 State of Nature report states that monitored wildlife has declined by 19% since 1970, and that the UK now sits in the bottom 10% globally for remaining biodiversity.

We will raise money for an animal hospital in Africa or criticise poorer countries for failing to protect their environments, while doing too little on our own doorstep. Take deforestation, for example. I remember growing up being told that an area the size of Wales was cut down every year in the Amazon, and that this was a crime against the planet. Yet we too exploited our own resources long ago, and in the UK, we have lost large areas of woodland and ancient habitat. We should be saying, learn from us, look at the problems deforestation and agricultural intensification caused here, and do not repeat our mistakes. Instead, too often, we lecture and berate. The rapid climate change we are facing is inseparable from the Industrial Revolution, in which Britain was a prime mover. This is still broader and more grandiose than Derek Gow’s point, but I think it adds context to the difficulties he and other conservationists face. For a nation of animal lovers, we can be strangely reluctant to love our own wildlife with the same intensity that we reserve for nature in more exotic places.

The second area to explore is the controversy in Gow’s work, not the ambition itself, but the method and the precedent it can set. His work is backed by strong evidence-based science, but do his successes encourage less well-thought-out ideas to take root? Some wild beaver populations began through illegal or accidental releases. Natural England monitors reintroduction and rewilding projects for good reason, but is the regulatory noose too tight, stifling people like Gow who have the science, money and willingness to make meaningful change?

This is the necessary point that the bureaucracy steps in, who decides which species are reintroduced and which are removed, what are the criteria? This is a prudent, safe approach, we do not want another disaster like the release of North American Mink into the countryside by ill-informed well-wishers. Britain is already awash with invaders mostly invited in with open arms. I don’t mean the Grey Squirrels, Deer or Gamebirds released but I refer to gardens. There are an estimated 2.8 million gardens in the UK and they account for 4.8% of the land cover and the majority are full of non-native species. So, in what way can we say that one species belongs and another doesn't, the answer is balance, does a species fit into an ecosystem, does it fill a niche without removing another species. I think this is a pretty good standard.

Rewilding needs to happen at scale, and that is difficult to achieve. Gow’s land is 300 acres, while Knepp covers a staggering 3,500 acres, yet even these places are small when set against the scale of Britain’s depleted landscapes. To be truly effective, rewilding has to move beyond isolated reserves and private estates into connected habitats, river catchments and whole landscapes. Otherwise, we risk creating impressive pockets of recovery that remain ecologically fragile because they are surrounded by the same pressures that caused the damage in the first place.

That old reserve-design debate, single large or several small, still matters. In the UK we have often relied on the second model: a patchwork of small reserves managed by organisations such as the Wildlife Trusts, the RSPB and the National Trust. Those places are invaluable, but they cannot carry the entire burden of nature recovery on their own. If rewilding is to move from inspiring example to national strategy, it needs cooperation across farms, estates, councils, conservation bodies and communities. The question is not just whether Britain cares about nature. The question is whether we care enough to make room for it.

Perhaps that is where the Radical interview left me, impressed by Gow’s impatience, drive and diligence, sympathetic to the need for safeguards, and convinced that the larger question is not whether rewilding is possible but whether we are prepared to tolerate the messiness of it. Nature recovery will not always look tidy, convenient or bureaucratically comfortable. If we want beavers, storks, water voles and richer landscapes back, we need more than admiration for pioneers. We need the courage to let some of their ideas shape the mainstream. Is Derek Gow a radical, maybe but he is the kind of radical we need now to move nature conservation forward and challenge modern conventions.

 

Beak Tooth and Claw by Mary Colwell - A review

 Most natural history books I read and review invite superlatives about charm. Mary Colwell certainly writes with charm, but the content of this book is far from charming; in essence, it is a book about death, and death at a staggering scale.

Beak, Tooth and Claw is an exploration of life alongside predators in Britain. Whilst this is the book's main theme, the book highlights the wider natural history issues of our relationship with the world and our place in it, or perhaps more accurately, our impact upon it.

The book is structured as a series of case studies looking at the fortunes of a number of predatory mammal and bird species. The introduction sets the stage well, exploring what predators are both historically, psychologically and philosophically. Consider, for example, that even the humble Blue Tit is both predator and prey. Each of these species is in conflict with us in some way, and usually it comes down to money, either the money lost when livestock is killed or believed to be killed by the predator or the money gained from shooting or hunting.

Inevitably, Colwell discusses the darker side of predator control, including fox hunting and shooting, but she seeks to understand the issue without prejudice, several times meeting members of these communities. She makes every effort to present both sides of the argument while still prioritising fact over sentiment. This approach lends credibility to the discussion, although I do not feel the book offers a firm conclusion. Instead, Colwell ends with a chapter on hope, acknowledging the benefits of rewilding and reintroduction. Some may call this cowardice, but I would frame it as a more respectful thought piece: one that presents information clearly and uses careful prose to illustrate the issues rather than force a verdict.

The book offers several key takeaways. First, it highlights the passion and dedication of the many conservationists who work tirelessly to improve the fortunes of British wildlife. It also exposes the ever-present drive for profit, both in the corporate world of big business and at the local scale. The biggest takeaway for me, however, was the complete disconnect between the modern British citizen and the landscape in which they reside.

Predator populations rise and fall; it is natural, as anyone who has studied the Lotka-Volterra predator-prey models will understand. In a functioning ecosystem, species thrive and decline within a dynamic equilibrium, a shifting balance. Interfere with that balance and you create something new. Britain's lack of apex predators, for example, has contributed to a booming deer population, which then needs control, often through hunting. We have knocked over the dominoes, and they are still falling. To continue the analogy, the dominoes can never be put back exactly where they were. Even if we stopped all nature degradation and reintroduced every missing species, the result would not be the past restored. Whatever was, was.

That wider imbalance is not abstract to me; it is visible in the changes I have seen in familiar species over the course of my own life.

In my lifetime, I have witnessed many changes in predator numbers. Red Kites, following reintroduction, are now as common in Warwick as they were in Aberystwyth 25 years ago. Buzzards, once absent from Warwickshire, are plentiful. By contrast, I remember seeing a Kestrel hovering over almost every motorway as a child; now, those hovering birds are a much rarer sight.

One story I felt was missing from the book was the arrival of mink in the UK and its effect on our waterways. It would have served as a useful juxtaposition to the chapters on lynx and wolf: while those species raise questions about reintroduction, mink show how dramatically an introduced predator can reshape ecosystems when it arrives without the cultural, ecological or practical preparation needed to live alongside it. Much has been written about the reintroduction of lynx and wolves, and while I think lynx are a more viable option than wolves, the biggest obstacle remains the collective psyche of the British public, conditioned for generations to live without large predators. There is no longer the cultural knowledge.

People can live alongside these species; Scandinavians and many other Europeans do. But in those places, large predators have remained continuous and contiguous with the native population. The folktale side of these animals is paired with practical, pragmatic knowledge of how to live alongside them. That cultural ability to coexist is something I think would be immensely difficult to achieve in the UK. We are so removed from our 16th-century selves that coexistence with apex predators is nigh on impossible.

For readers interested in British wildlife, rewilding, predator politics and the uneasy moral terrain of conservation, Beak, Tooth and Claw is well worth reading. It is less a neat argument for or against predator reintroduction than a thoughtful account of why these debates remain so difficult.

Beak, Tooth and Claw is an easy, comfortable and thought-provoking read. It is well researched and discusses many of the problems endemic to modern conservation through the lens of Britain's predators. More importantly, it leaves the reader with the harder question: not whether predators belong in our landscape, but whether we are still willing, culturally and politically, to make room for them.

You can purchase the book here

The sound of nature

 

 In my continuing efforts to catalogue all the species on my patch, I have splashed out on another piece of surveying equipment. My trail cameras have given me a detailed insight into the mammals using the site — with one obvious exception: bats.

Bats are nocturnal, small and fast, which makes accurate identification difficult. I have seen bats on site and recorded some with my mobile bat detectors, but that depends on me being out in the field every night and staying there long enough to pick up everything. After all, not all bat species fly at the same time of night.

I began by looking at devices sold by Wildlife Acoustics, such as the Song Meter. That got me interested in using sound to identify species. These devices can now help identify bats, small mammals, some insects and birds. Further research led me to the BTO acoustic pipeline, an ambitious programme that analyses sound data and uses machine learning to identify species.

From there, I started exploring the options in earnest, looking at Wildlife Acoustics, Titley and finally Batlogger. After much deliberation over recording types and price, I opted for the Batlogger S2 detector.

The Batlogger S2 is a static logger controlled by an app. The device is small, well-constructed, and easy to use, putting it head and shoulders above the PippyG I had been trying to get to grips with. That said, for the price and with a little perseverance, the PippyG is a good bit of kit — as long as you can understand how to operate it.

The Batlogger app makes setting up the device simple. Strap the unit to a tree with a clear recording area, then activate it using the app. The app works on Android and iOS, connects to the device via Bluetooth, and records its location using the phone’s GPS. You can also schedule when the logger is active. It has an internal SD card, so there is no need to keep swapping cards in and out, and it charges via a lead to your computer, which is also how you download the data.

The data is saved as .wav files, which then need to be analysed. I have used the free version of BatExplorer, but because I am not trained in acoustics or bat identification, I found it difficult to use. It looks like a powerful piece of software, with several ways to present the data, but I needed something a little more approachable.

After experimenting, I opted to use the BTO acoustic pipeline, partly because the analysis is accessible and partly because my data can contribute to wider research, as my bird records on BirdTrack do.

Acoustic analysis is very new to me, but the data produced by the pipeline is clear and approachable. Each automatic identification is given a probability score between 0 and 1. Reading through the literature, the suggested threshold appears to be 0.5, with anything below that disregarded. The statistician in me feels that 0.5 is too low, especially given some of the species suggested in the results. So, for my own analysis, I set two additional thresholds: 0.75 as an amber level, where a species has a good chance of being correct, and 0.9 as a green level, where I felt the identification was acceptable. To help with this, I aggregated the data from the two surveys I ran in June and displayed the results as boxplots. This allowed me to look at the median, mean and interquartile ranges for each record. The final factor I considered was the number of contacts.

So, what species did I find?

After aggregating the data into Chiroptera and other species, for bats at the 0.5 level, 9 species were identified; at the 0.75 level, 8; and at the 0.9 level, 6.

I think it best to use a sensibly high figure as an ID value, so I am only accepting Common Pipistrelle and Soprano Pipistrelle as definitely present on the site, with Brown Long-Eared Bats, Leisler's, and Noctule as possibles. I now plan to review the literature to better understand the ecology of those species at my site. 

The non-bat species, as shown below, offers the most interesting records, but one for which, despite the high probability value, I have the least confidence.

In this analysis, only the Brown Rat fails to reach even the lowest level of acceptance. The other rodent species, like the Wood Mouse and Yellow-necked Mouse, are expected. Wood Mice are widely present on site, and although Yellow-Necked mice have not been identified, they are possible; it's hard to differentiate the two in trail camera footage. 

Harvest Mouse was a very surprising record, and I need to understand their audiology and ecology to determine whether they are likely to be present on the site. There is a section on my patch that is suitable habitat, but it is not in the detector's location.

I know that Bat detectors can detect grasshoppers and crickets, but I would have been sceptical of the presence of two species of Bush-cricket had I not identified a Speckled Bush-cricket nymph only the week before.

Lastly, there are the shrews; they communicate in ultrasound, and so it makes sense they would be detected. Both Common and Pygmy Shrews have been recorded on the site, and Water Shrews are suspected. 

This information gives me some interesting species identifications that warrant closer investigation. I now need to find ways to confirm the presence of Water Shrew and Harvest Mice.

I have only used the logger twice, and I need several more runs and practice with it before I feel more confident. I also really need to understand animal sounds better.

With every new device, my understanding of my patch increases.

An early feast

Today, whilst out birding, something caught my eye. I have started visiting Warwick Racecourse more often this past year, mainly to build up a species list for the site and to get some nice photographs of different birds. 

At this time of year, I am usually focused on the Skylarks and the returning warblers; however, today, what caught my eye first was a flock of Starlings. Starlings are not unusual on site. They are present all year round in small flocks, usually on the short turf by the football ground. Here they potter over the grass, looking for insects and probing for leatherjackets. Today, however, they were further over near the water channel. They sat along the fence line, some of them shooting into the air, hovering and then returning to the fence. If I couldn’t see directly that they were Starlings, I would have identified them as stocky flycatchers, twitching into the air, fluttering and returning to a perch. It was this odd behaviour and that thought of the flycatcher that held the answer. 

Taking a moment to look around me, I noticed that the air was filled with black flies. Flies are often a very overlooked taxon, unless they are flying around your food, but they are incredibly important ecologically. The flies I could see were familiar to me. 

They were jet black, some about an inch long. They floated in the air with their legs dangling, looking like some kind of drone. They seemed to bob on the air currents, settling occasionally on vegetation. These flies are known as St. Mark's Flies (Bibio marci) or the hawthorn fly. They are called St Mark’s flies because their emergence flight period usually coincides with St Mark’s saint day (25th April). 

Image from Warren Photography - https://www.warrenphotographic.co.uk/28027-st-marks-fly-in-flight

The fly is known for its spring appearance. Its larvae live in the soil, feeding on roots and decaying vegetation before pupating into their adult forms, which then take to the air, slowly drifting in swarms with their legs hanging down. This stage is short-lived, lasting perhaps a week as they search out a mate. During this week, they sustain themselves by feeding on the nectar of fruit trees and hawthorn flowers, making them important pollinators for these species. 

In many ways, this display of floating dancing flies is a terrestrial form of that exhibited by Mayflies over our rivers. These swarms form an important food source for many species. The Starlings had identified this and left their usual spot to take advantage of the glut of food.

It's one of nature's miracles, the ability of such tiny organisms to synchronise and emerge together. Sometimes it's the small things that reveal the most.

An upgraded Mostela

 

I have embraced camera trapping as a medium for observing and recording nature. What started as a whimsical addition to my arsenal of ecological tools has turned into a passion. I have been running cameras for over 10 years, have experimented with several techniques, and have even published a book on the topic.

One of the most interesting tools in camera trapping is the Mostela. I have blogged about this device before. Mostelas are designed to improve the detectability of small mustelids such as Stoats and Weasels.

Mostela as detailed by the Vincent Wildlife Trust 2022 (image courtesy of Vincent Wildlife Trust)

They are essentially a box with a drain pipe entrance that contains a camera. They can be baited or unbaited. The theory is that these spaces will be used by small mammals such as voles, mice and shrews; they will visit the site for food if baited or just investigate it. Their continued presence creates a scent trail that Weasels and Stoats will follow when hunting.

Weasel recorded in the current fixed Mostela in 2025

Raw Components

In reality, I have had little success with capturing images of Weasels and Stoats. I am not entirely sure Stoats are resident on the site, in person or on camera. Stoats have only been recorded once since 2015. Weasels, however, are resident, but due to their speed, they are not easily detected on camera. On Otter Cam and the mostelas, they have been recorded once a year, whilst the hedgerow camera recorded them on average twice a year.

The greatest benefit I have found is not in collecting mustelid data but in observing the small mammals. Small mammals can be recorded with standard camera placement, but better identification is achieved with small-mammal rigs and mostelas.

I have used home-built mostelas for over two years, as well as purpose-built ones purchased from the Netherlands (An expensive approach!), and now feel like I want to experiment with the design.

Assembled

One drawback of the mostelas is that, during the daytime, the closed chamber makes it still very dark and often requires infrared to make any visitors visible, making the visitor's pelage colour hard to see. This can be important in identification. To counter this, I am experimenting with a translucent lid that should give better colour clarity during the day.

I have also removed the base plate to reduce costs, provide a more natural view, and allow the camera to be placed more effectively. Often, the best camera positioning involves tilting the camera down. With Gardepro and Bushnell cameras, which are my preferred brands, the lens is often quite high on the device, meaning that individuals moving closer to the camera are often missed or hard to see. Without a base, it is possible to dig a trench for the camera to sit in.

To build this mostela, I have used marineplywood that I bought online pre-cut to size. For the entrance tubing I am experimenting with two entrances opposite to each other using bend fixtures bought from Amazon. This cuts down on the difficulty of cutting and sealing a length of drain pipe.

I have tested the principles in the back garden but this weekend I will install it in the wild to replace my existing mostelas that is slowly disintegrating.

58 and counting

 

Today is day 88 of the year; over the last 88 days, I have seen 58 different bird species.  Just over halfway through this year's attempt to complete the Warwick 100. This is the local attempt for local birdwatchers to see 100 different species over the course of a year. I decided back in January to keep a species list and track the number of species I recorded week by week.

This graph shows the week-by-week increase in species, essentially a Species Richness curve.

The most interesting species seen so far have been:

Northern Shoveler

Mandarin Duck

Gadwall

Oystercatcher

As part of this effort, I spent last weekend scouring Warwick.  On  the Friday, I visited the Chase Lakes, the Hopyards, St Nicholas Park and finally the flash at the Saxon Mill travelling along 5 Km of the River Avon. On Saturday, I visited the Racecourse, and on Sunday, I went to my normal patch. 

In total, over the 4 hours of survey time, I recorded 46 species. This shows how quickly a species list can be built up over a relatively short period. The key is to visit as many different types of habitats as possible. We are lucky in Warwick to have woodland, farmland, grassland, rivers, lakes, and reedbeds.58