Friday mystery object #444 answer

Last week I gave you a couple of skulls from the collections in the Dead Zoo to have a go at identifying:

It’s pretty obvious that they are rodents, based on those paired incisors. But there are a lot of rodent species out there…

These are small and, based on the size, we can immediately rule out all anything bigger than a Brown Rat. The anterior portion of zygomatic process, where it meets the maxilla (the front parts of the cheek bones) are broad and triangular, narrowing to very fine arches where it meets the temporal porocess (the rear part of the arch of the cheek bone). This is something I associate with voles.

The teeth are also distinctively ‘voley’ with their zig-zagging cusps.

There are still a lot of vole species out there, but if you’re familiar with identifying specimens from owl pellets in the UK you’ll probably recognise that the specimen on the left has a very distinctive second molar, with a small fifth cusp. This is a tell-tale indicator of the Short-tailed Field Vole Microtus agrestis (Linnaeus, 1761), while the more rounded cusps of the specimen on the right are more in keeping with a Bank Vole Myodes glareolus (Schreber, 1780).

So congratulations to Chris Jarvis in the comments, and to the Scarborough Museum and Galleries Collections Team on Twitter, who managed to leave sufficiently clear but cryptic clues to the identity of these skulls:

I hope you enjoyed these smol skulls and the pointers provided to separate them.

Friday mystery object #429 answer

Last week I gave you this taxidermy specimen from the Dead Zoo to have a go at identifying:

It turned out to be easier than I suspected, because an image of this specimen just so happens to be used on the Wikipedia page for the species. This was a bit of a give-away for anyone who even got close to the type of animal this is. So let’s figure out what general type of animal we are dealing with.

First of all, it’s fairly clearly a rodent when you look at those incisors. I suppose incisors like that could be found in one of the lagomorphs (rabbits, hares and pikas) but they all have much larger ears in relation to their bodies (even the relatively shorter eared pikas have much bigger ears than the mystery specimen).

There are a lot of rodents, but this one is quite large, which helps narrow things down. The majority of large rodents are either semiaquatic (like Capybara, Beaver and Coypu – and it’s not one of them) or spiky (a variety of unrelated porcupines from the Old and New Worlds). Then there are the maras, agoutis, and pacas (plus relatives), but they all tend to have almost absent tails and quite long legs compared to the mystery object.

There is another group that has some moderately large members though – the hutias. There are 10 species living on various Caribbean Islands, with a relatively wide variety of adaptations thanks to island effects. In particular their tails vary from being almost absent to being quite long, thick and prehensile. Checking tails should pretty much seal the identification. Of course, it’s much easier to spot when there’s a photo of the same specimen, on it’s quite distinctive base, with a label:

Image by Illustratedjc, 2015

So well done to everyone who figured this out that this is the Bahamian Hutia Geocapromys ingrahami (J.A. Allen, 1891), especially if you didn’t spot the Wikipedia entry!

Friday mystery object #427 answer

Last week I gave you a nice skull to have a go at identifying:

It proved to be more tricky than I thought, but I think that may be because there is a skull image on Wikimedia that may have misled people searching for a comparative skull of this species.

This is the skull of the humble Guinea Pig Cavia porcellus (Linnaeus, 1758), but if you tried searching for Guinea Pig skull, you may have seen this image:

Clearly this is not the same species as our mystery object – the incisors alone are an absolute give-away, with their striking orange enamel and the their much greater size. Those big incisors also bed deeply into the mandible, creating a pronounced ridge at the base of the mandible that props the entire skull at an angle. This one is the skull of a Coypu, regardless of the Guinea Pig identification given on the Wikimedia page.

There were also quite a few suggestions that the mystery object might be a Capybara, or one of several other South American rodents. The size suggests it’s not Capybara – I suppose a very young Capybara might just about be small enough, although they would certainly have less pronounced muscle scars and more open sutures.

There are plenty of other South American rodents, but most of those of a similar size and overall shape have a much more V-shaped exit to the nasal passage in the palate, rather than this very open and U-shaped structure.

When identifying skulls, it’s generally best to rule out the most common and likely species first, since this can significantly speed up the identification process. This is why misidentified comparative specimens can be a problem, so always try to check more than one example. I’ll certainly be suggesting an edit to the misleading Wikimedia entry to help prevent this issue in future, but this isn’t a criticism, since nobody is perfect and I know I’ve made mistakes myself in the past, especially early on, so I’m trying to fix them retrospectively!

Paolo’s Pest Post #1: Rats

Spring is in the air and the burgeoning of new life all around us is not restricted to daffodils and baby birds, it also includes some less welcome organisms. Working in a museum means you really need to be aware of pests. A serious infestation can reduce objects to piles of dust in a worryingly short time. Every museum has pests, as does every house – they are impossible to eradicate completely and it’s a waste of time trying since they are mobile and can reappear just a few days (or even hours) after you’ve just finished exterminating their predecessors. Pest populations require constant management rather than blitzkrieg if they are to be kept at levels where they don’t pose a problem. In museums this is called Integrated Pest Management (IPM), at home it’s called housekeeping.

The majority of IPM is making sure that there isn’t enough food lying around to provide pests with the rations they need to explore your museum or home. If the pests can’t find food, they have no reason to hang around. Most of the food that pests find will be in the form of small edible particles (crumbs from your lunch, hair, skin cells, dead flies, pet food, etc.). This means that foodstuffs should be restricted to easily cleaned areas that are separated from areas containing vulnerable objects. Regular cleaning also needs to take place everywhere to remove the accumulation of organic waste that constantly builds up. Sometimes this isn’t easy, especially when buildings have been designed without pest prevention in mind:

Security grill in front of a window, making the sill difficult to clean

Of course, our museums and homes also have a standing supply of food for pests in the form of taxidermy, wool, paper, wood, dried goods, carpets, clothes, etc. This is what we are trying to protect, so we can’t simply remove it all. Instead, we need to keep a lookout for tell-tale signs that pests are busy munching away at these items, so that particular infestations can be dealt with before they spread.

Vigilance is key – everyone working in a museum or living in a house should be aware of what constitutes a pest and they should know where to report any sightings of pests (be it to Collections Management, Facilities Management, Conservation, or mum/dad). Whoever is in charge of dealing with pests should also be making sure that they carry out a bit of extra work, either by using monitoring traps to keep track of pest distributions so hot spots can be detected, and/or by keeping an eye on windowsills – a prime location for spotting pests of the insect kind. It is also useful to keep an eye open for the little signs that pests leave lying around – droppings, frass and characteristic damage.

Although some pests may have had a population in your building for as long as you’ve been there (or longer), most will have found their way in more recently. Points of entry are varied and often uncontrollable (you can’t check the coats or bags of every visitor for hitch-hiking beetles and moths), but where possible there should be checks in place that reduce the ability of pests to get into a building. A quarantine area is ideal (dare I say essential) for controlling pests that can be transported on museum objects, but at home it may simply be a case of checking that your newly purchased bunch of flowers or bag of flour isn’t crawling with beetles.

Various holes, vents and chimneys are excellent entry points for pests so it’s good to keep an eye on them – block up the ones that don’t belong there (like broken windows or holes in ceilings) and make sure that the ones that do belong (like air vents and chimneys) are kept clean and, where practical, protected with a mesh on the outside.


Part of what inspired me to start writing this was an incident at home that Melissa and I recently dealt with. We live in a basement flat, which means that we are likely to have certain types of pest finding their way into our home quite easily. In this case it was one of the most unpleasant pests you can get – we had a rat in our kitchen.

We knew that there was a rat in the garden, because we had seen it before. In fact, we have an entertaining video of it chasing magpies right under the nose of a disinterested local fox one Sunday morning:

However, a rat in the garden and a rat in the kitchen are two different things. Rats carry a host of nasty diseases and they are incredibly destructive because of their droppings, urine and need to gnaw – rats gnawing wires are a common cause of fire. There’s some useful information about problems caused by rats here. Our rat appears to have entered through a hole in the wall that takes the waste pipe from our washing machine – unfortunately the hole is much bigger than the pipe and the rat must have squeezed through the gap, something that rats are very good at.

We had a suspicion that a something was amiss when Melissa heard rustling and caught movement out of the corner of her eye one evening. The next day I also saw something fleeing behind the fridge when I walked into the kitchen and I thought it looked a bit too big to be a mouse – I was also fairly sure I had seen a long scaly tail. That clinched it, so we immediately did a fairly deep clean of the kitchen and we cleared out all the boxes and bags crammed into our airing cupboard, which is in one corner of the kitchen. On removing everything from there I spotted that the insulation around the boiler had started being gnawed to make what looked like nesting material. There were also droppings that were too big for a mouse (between 10-15mm):

Rat dropping

Whilst clearing out the airing cupboard our unwelcome guest was spotted as it dashed for cover, reconfirming the evidence that it was a rat. Obviously we were not pleased. Once everything edible was secured in containers in upper wall mounted cupboards or hanging from wall hooks, we shut the kitchen door and hoped the rat would stay put until it could be dealt with. Fat chance – we found fresh droppings in the hall after the rat had squeezed under the kitchen door. Our deep cleaning had probably removed enough accessible food from the kitchen to force the rat to roam further afield.

The advantage of this was that it suggested the rat was hungry and that there was enough disruption from our activities to have forced the rat out of its comfort zone. That discomfiture of the rat was an important, since rats are neophobic – they don’t like new things in their environment. Reducing the available food meant that the rat was forced to explore further and by altering its environment (i.e. removing most of the cover it relied on) we were forcing it to deal with changes, which meant that it would probably become familiarised more quickly with the traps we baited and put down at around the same time.

We chose break-back traps over poison for several reasons:

  • some rats have learned to avoid poison (although some are also trap shy)
  • there is no control over where the rat dies, so it could expire in an inaccessible place and then stink the flat out for weeks while it decomposed, incidentally providing a source of food for insect pests
  • if the poisoned rat went back outside it could well be eaten by something else, which could be harmed
  • neither of us are happy having poison hanging around the house, particularly in case we are visited by friends and family with younger children
  • I have ethical concerns about the suffering an animal experiences before it dies – I think a quick death is preferable to a slow one, and I consider poison to be too slow

A good strong break-back trap seemed to be the best option, since there is greater control of where the rat is killed and a trap is far more easily disarmed and tidied up than poison – it’s also a quick death for the rat (though see below). Live traps can also be used, although for rats I think they are inappropriate since releasing a rat in a new location strikes me as being irresponsible to residents of the area in which it’s released, and it’s pretty stressful for the rat.

Glue boards are also available for trapping rats – these are obviously a slow way for the rat to die, unless they are checked frequently and you are willing to kill the rat yourself. We did use a sticky board under the kitchen door when it was shut (I had a rubber mallet ready to despatch the rat), but that was more as an effort to reduce the rat’s movements within the house than to trap it.

I should make sure I mention that break-back traps need to be checked regularly – sometimes they can go off without killing the rat, merely trapping it (and injuring it) and sometimes the bait can be removed or material from ratty activities can jam the mechanism, making it less effective. Although I was aware of this, I was a bit surprised when I first checked the trap and found a scouring sponge right in the jaws near the hinge:

The snap trap was initially baited with chocolate (rats really like chocolate), but that was switched to nuts and raisins as soon as I realised that bitter dark chocolate that we had in the house was probably not quite the sugary, fatty confectionery treat that a rat would be after. The change of bait seemed to work out well, because we had the rat in the trap a few hours later:

Since the rat was a bit crushed from the powerful jaws of the trap I decided not to bother skeletonising it or getting it taxidermied. Instead I checked the local council website to find out what their disposal requirement was – double bagging and putting it in with the household waste – so that’s what I did.

All in all an unpleasant business, but it only took two days from the first sighting for the rat to be dealt with. Our next action is to contact our landlord to get the hole sealed up properly and we will probably clear out the crumbs from the toaster and bread-board a bit more often, since that’s what the rat seemed to be subsisting on.

If you have a rat then I recommend that you clean and disinfect thoroughly, make food as inaccessible as possible (easier said than done since rats can get through tiny holes, climb well and gnaw through plastic, wood and even concrete with ease), check where the blighters are getting in and work out where they are going, so that you can take steps to stop them. Most councils offer a pest control service to deal with rats (often it’s free), so if you don’t feel up to dealing with the rats then you’re probably best off contacting them. That said, I personally find it’s more effort to deal with contractors in my home than it is to kill a rat.