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Animal Homing

  1. Sep 3, 2017 #1
    I have been reading about the theory of magnetoreception which may partially explain the homing ability of pigeons. Many studies are inconclusive, so I am wondering if I can extend this theory to other animals, specifically to the Beech Marten (aka Stone or House Marten, Martes foina).

    This animal is a pest in continental Europe, where it likes to inhabit the roof space of houses. It stinks the place out, so you are forced to get rid of it. I use a legal trap and release the animal in a wooded area.

    This time it seems I made a mistake because I released the animal 25 km away. Afterwards I learned from various sources, all experts agree that I should have released it at least 60 km away, otherwise it will surely come back home. I would like to assess the likelihood that it can do this, in unknown terrain in the dark (it’s a nocturnal animal).

    I transported the animal in a very round about route. It was always in the dark trap box and it could not have known it was being transported at all, could it? How can it know with all the twists and turns of the route that it was let out 25 km north of home?

    So when it was let loose in an unknown place, how is it supposed to know where it is in relation to home? It stretches my imagination to believe that over such a short distance as 25km an animal can use the earth’s magnetic field alone to know where it is in relation to the magnetic coordinates of home. So is the 60 km safe minimum to be believed? I am suspicious of this number because the self-appointed experts don’t mention what lies between (towns, rivers, highways, etc.).

    If I first drive round in circles a bit, would that fix the problem? Do homing pigeons find their way in the dark without training and being taken to a new starting point blindfolded?

    In Europe the revere of a Beech Martin is about 2 square km, so it would need to approach this area before it gets local cues. Perhaps say about 5 km from home before it gets olfactory cues. Or am I underestimating the sensitivity to olfactory cues?
  2. jcsd
  3. Sep 3, 2017 #2

    jim mcnamara

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    This article suggests that bird navigation is a multi-function affair, where the bird builds a map for a destintation based on visual and olfactory cues such as stars, the sun angle, atmospheric odors, and possibly the magnetic field of the earth. All of this is based in the hippocampus (area in the brain).

    Driving in circles will not help. What works for one species may not work for others in terms of distance.
    Birds apparently build the map a posteriori - after the fact of relocation. Bird species also have differing visual abilities. So what works for species A may not work for species B.

    So yes, it is possible that letting the captured bird go too close to home could be a problem. Given that arctic terns can navigate 19000 km and return to a small nesting area kind of eliminates that species from the list of birds you can relocate successfully with a reasonably easy to attain distance.

    Is there no kind of legal deterrent? Removal seems "iffy" to me. Convincing them to leave seems a lot more reasonable.

    Example: Rock doves (pigeons) are a roof pest. There are many kinds of physical deterrents available you can install on the roof.

    Google for some examples:
    Bird wire, plastic bird spikes for the roof, sonic bird deterrent, predator statues. All of these are legal in even the most restrictive cities in the US. They simply annoy the birds and they leave.
  4. Sep 3, 2017 #3


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    I like the deterrence approach.

    We have a large population of raccoons in our area and large roving families of them making daily (nightly actually) rounds through the neighborhood.
    I have a pond in the backyard (fenced) that used to be under attack from them (they seem to really like destroying emergent water plants).

    I (and similarly inspired neighbors) have considered a variety of options:
    • trap and transport to a distant area (about 10 miles is considered good)
    • trap and kill (a friend gasses them with car exhaust, pretty quick but not for me, I usually only kill lab animals or food (like fish))
    • exclude from large areas (not feasible with all the trees etc)
    • exclude from smaller areas (I use the smallest available electric fence (~$40 at a local farm supply store) which I have enclosing the pond, works well)
    All of these are legal here.

    Without concerted elimination efforts throughout a wider area, the population of raccoons (we had a family of 8 patrolling our neighborhood) will merely move into any smaller area from which they are eliminated.
  5. Sep 4, 2017 #4
    Thanks for the interesting article. It’s mainly about birds, which are mobile over a large area, can look down from a great height and can use airstreams to identify the source of odours. Land animals do not have these advantages. The article draws me to the conclusion that in the case of my Marten, odours are key. Here one problem is that wind directions vary quite a lot, and another problem is that there is an industrial town between my Marten’s home and where it was set down, which will surely block, distort and mask odours coming from the other side of town.

    The article does not explain how magnetic variations and their incidence to gravity can be used over very short distances, as I am assuming that these variations are exceedingly small within a range of 25 km at constant altitude on the earth’s surface where there are no anomalies. This method is more believable as applied to high flying birds over long distances.

    Yes there are legal deterrents. It depends on the country. In Switzerland where I live Martens fall under the hunting and fishing laws which are very complicated regarding methods of hunting, seasons, licenses and examinations to get a license. I am using a legally allowed trap at a legally allowed time of year. Germany is an interesting case where Martens and many other pests such as moles are so tightly protected that you had better not talk about it. If your grounds are invested with mice, you are not allowed to poison them. The product which was previously approved for outside is now only approved to kill mice inside buildings. So the manufacturers have relabeled the product. In Switzerland you can fish from the shore of a public lake without a licence, but to fish from a boat on the same public lake you need to pass an examination and then get a licence. Many people fish from their jetty. They don't care if it's legal or not. Europe is regulating itself into oblivion. Nice place though.

    You are not familiar with Beach Martens because they are rare in America. Trying to annoy a Marten or convince it to leave your roof space is a joke. I have blocked all possible entry points with wire mesh. The only possibility remains that they crawl under and leverage up heavy tiles which you would not think possible, especially since the tiles are linked together. You would also think it impossible that an animal could produce such a strong stink that the room under it is unusable even with no hole in the ceiling.
  6. Sep 4, 2017 #5
    The 10 miles interests me. How did you decide this? How do you know it is far enough? What is your source?

    I am not familiar with problems associated with raccoons, but I think that they are nice animals and should be relocated if possible.
  7. Sep 4, 2017 #6
    Here is a study, but I don't have the full text. It does not say whether the maze was openair. This extract suggests to me that most cats do not use magnetoreception. There are a lot of anecdotal stories about long-distance cats (and other animals such as dogs), but it seems that most returning pets do so from a relatively short distance of 5-10 miles. So I am wondering if magnetoreception in animals is a highly variable ability, unlike migrating birds and butterflies etc. which do it regularly for long term survival reasons.

    "Precht and Lindenlaub (1954)* tested the ability of cats to correctly orient towards home at various distances. The cats were carried in sacks and placed in the center of a maze which led to six equally spaced exits. The majority of cats did not wander around the maze, but instead quickly chose an exit (though they were not actually allowed to leave the safety of the maze). They found that the cats’ homing sense was only fair and directly related to their distance from home. At distances of 3.1 miles (5 km) from home, 60% of the cats chose the exit that faced the direction of their home, and at greater distances, they did not appear to know the direction of their home."
  8. Sep 4, 2017 #7


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    This is information that a neighbor got from some local official who gets consulted about raccoon issues. I have no idea where it came from, but it is presumably (hopefully?) based on experience, since its a common problem here. This should be something that could differ depending on the species of animals involved and perhaps the terrain.
    If there is a local breeding population, removal does not look very promising to me as a long term solution.
    Another possibility might be some kind of chemical deterrent, if it is tolerable by people, pets, etc. There are specific substances that can be used to attract or repell insects (usually derived from plants) and are used for control purposes. We used a local guy who does this for controlling roaches and silverfish in a large research fish facility where we did not want toxic chemicals (due to the 100,000 research fish in the same room).
  9. Sep 4, 2017 #8
    I agree that trapping and relocation is not a long term solution against animals which have a preference for living in roof spaces. My problem is compounded by the fact that I have no access to the interior of my roof as it is completely sealed, or so I thought.

    Apart from Martens I also have a more frequent problem with mice which make a lot of noise in the night. I get rid of the mice by laying Brodifacoum in the gutters in dry weather. I have used an infra red camera to observe the mice, but it did not reveal any entry points. Next time I will try to use the camera on the Marten, but I have no idea which part of the roof to point it at.

    Brodifacoum is pretty powerful stuff (Vitamin K antagonist anticoagulant) so I have to be careful with the dog. It is also used against Possum, so probably it would take a Marten down too, but for the time being I prefer relocation. The trap works well. My wife said that she doesn’t want a dead Marten in the roof, live ones are bad enough. In Switzerland services like vermin control cost a fortune and I don’t see how they would do it without making holes in the roof. The roofing contractor has advised against this.

    Martens drive people crazy and various deterrents and repellents have been used and it’s reported everywhere that they don’t work. Examples include diesel, deodorants and loud music. The Martens love it. A large cat might work if it could stand the stink, but I can’t put one in the roof.

    If there is someone here who knows an available substance which drives away vermin like possum, weasel etc, and is proven to really work, please post.

    Meantime I am inclined to believe that 25 km should be enough.
  10. Sep 4, 2017 #9


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    Mice can easily get through a crack of about 1/4 inch (~6 mm, probably the height of its skull).
    I was chasing one down a hall once and it ran under a closed door (~1/4" space at the bottom) at full speed.

    Roofs (as constructed in the US) have built in ventilation to permit air flow under the top roof elements.
    Some are just cracks, others are larger holes covered with screens or metal mesh.
  11. Sep 4, 2017 #10
    Yeah, and not only mice, Martens as well. Amazing that builders and roofers who live and work in the country don't seem to know these these things. Total incompetence that my roofer didn't give me access. Then he came afterwards and charged me for covering up a few holes he had left which I could put my hand thru. Afterwards I wire meshed all round the gutters and chimney stack myself. Waste of time - I would have had to fine wire mesh the whole roof!

    My Stone Martens are called like that because they orginally lived in the small holes and crevices between rocks.
  12. Sep 4, 2017 #11


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  13. Sep 5, 2017 #12
    Excellent tip, thanks! It seems that this is an approved insulating method for roofs and walls in several countries. I would have to use it to seal the complete roof, which I am not qualified to do, so I will look for a contractor. I assume he will first have to remove all the tiles, so it will not be cheap. On the other hand a permanent solution if animals such as mice etc do not eat through it. I will have to check this point first. Mice are good at making holes when they want to.

    It could be that if all the tiles have to be removed first, then it would make more sense to cover the whole roof with wire mesh between the tiles and batons and the plastic waterproofing. Important is that the contractor does a 100% perfect job, otherwise any concealed gap is a potential entry point. Very tricky. Sounds like a complete reroofing job.
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