Hi. I was once part of a project that successfully used PIT tags on Eastern Chipmunks (< 100 g mass). I don't know if they would work on something as small as a pygmy shrew, though!

Hi! I've worked in a clinic where we used PIT tags in turtles. These are the PIT suggested from CITES and are smaller than PIT of dogs and cats. Size should be 1,5 mm x  7 mm. Hope it be useful. 

You can get RFID tags that are very small - try an internet search for micro RFID, and you'll find lots of useful leads.

Is currently already use PIT tag in  Microchiroptera.

For mammals this small I would not use even 8x2mm iso tags - so you are stuck with the modern 1-1.5x7 tags but...

read distances are miniscule and probably unworkable for wild animals - systems I've seen demonstrated require the tags to be within a few mm of the reader plate - effectively running directly over it with only thin skin between them - easy to do with the intended use - lab mice in the hand - almost impossible to enginneer in the field.  reliable reads of PIT tags is an often overlooked aspects of the use of the tech.

james

It seems that there are no smaller tags than 1-1.5x7. a diameter of 1-1,5 mm will work but the length of 7mm is much to big for such small shrews.

Seems there is no alternative to toe clipping.

We successfully used standard microchips for marking shrews, including pygmy shrew. They will live with it, but there is a big risk of injury. Moreover, they quite easy loose the tags, so toe clipping seems to be good alternative method. In some studies we mark small mammals using both chips and toe clipping. If you want to read small tags you need reader with big antennae otherwise you must literally touch the tags to read it. 

Have you considered a method like freeze-branding? 

I know that this method had been used on smaller mammals before. I have also used freeze-branding on hyraxes before...

There are some good leads here already on microchips, but you should also be aware that this method has long-lasting consequences for such small mammals and I would advise only to use as a last resort.  Micro-chips have been known to induce cancers in shrews.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2949435/

I agree with John that it can have a long-term effect and is rather unsuitable for studies on survival etc.

Richard Morris of Pharmasec in New Jersey and his colleagues have developed tiny p-chips that may suit your purpose.  The have been used to track lab mouse by injection into the tail.  The chips themselves are tiny, 0.5 mm wide, and fit onto the head of a pin.

Richard G. Morris, Ph.D. [email protected]

CEO

PharmaSeq, Inc.

11 Deer Park Drive, Suite 104

Monmouth Junction, NJ 08852

tel: 732-355-0100, ext 13

www.pharmaseq.com 

You might find this paper helpful.

I've used microchips to tag arboreal marsupials 150-300g (Trovan ID 100, Dimensions: Dia. 2.12; Length 11.5 mm (0.08 x 0.45 in.)), but I must admit I've never tried anything smaller. 

Consider though, if it's only a short term study, and you have an alternative marking method that is reliable, perhaps microchipping is not worth the effort and risk. 

Hi, we have used RFID micro  PITs for far more than 1000 small mammals (Microtus arvalis between 20-30gram) in laboratory and controlled outdoor experiments and made quite a lot of positive experience. We also used PITs on some shrews injected under the necks skin fold, but the cut made by the needle does not close as fast as in Microtus species and the PIT is lost more often. We also tried to use the smallest cable ties to fix PITs on cable ties, but the shrews´ head is often smaller than their neck so you can not close the cable tie real tight. There is also medical glue used to glue together woundings and cuts in the skin, so you might try to glue a PIT, but that does not hold to long. Besides the technical problems, shrews are the species most sensible to handling stress (and anesthesia if that is an option), some dying within minutes, so you have to have a lot of experience in pitting animals and have to be really quick if you want to do it in the field. For identifcation we used 20x20cm plate antennas reading a field of 30x30x10cm so we buried the 2cm in the ground and placed foraging stations on top to get the shrews repeatedly

I have used Trovan tags for Apodemus sylvaticus and also for different Crocidura spec. We injected the pits under the necks skin fold. Additionally we marked them also with fur cut. But similary as Thilo Liesenjohann wrote, you must be carefully as shrews are very sensitive for handling..but anstesia is also problematic. we had the best results with pitting them very quickly. You can learn the pitting in a fist step on dead animals.

I also use the Trovan ID100 for common dormice and inject these under the skin in the neck without using anesthesia. We do this with adults and young animals from 9-10 g onwards. We never had problems with infections from this. Sometimes they have a small bold spot for a while, but usually you don't even see the spot anymore if you recapture them the next day (they are very trap-happy even after microchipping...). We only had 2 or 3 times (from a few hundreds) that they lost the tag, but if you put it far enough under the skin it shouldn't emerge again.

and did you narcotised the small mammals before injection into the neck?

no, we don't narcotise them

Thanks for all your answers. I think the p-chip from PharmaSeq will be the best solution

”Is it possible to chip small mammals?”

more than sure

we are using markers even for recently hatched fish, so marking of terrestrial species should be no problem for You