I spent much of my working life travelling in rural areas. During that time I observed many instances where wild birds and animals had died after becoming trapped in fences.
I was reminded of this recently when I made the observation below.
https://www.inaturalist.org/observations/194081372
The animal in the picture is a greater glider, a species of gliding, arboreal marsupial which is a threatened species in Australia. It was obviously entangled in the wire where I guess it would have died a slow death. I have seen several species of gliding marsupial, fruit bats and birds caught in fences, however the most common animal to fall victim to stock fences seems to be kangaroo species. A kangaroo will try to jump a fence and will catch it’s foot on the top wire. As the animal trips forward the long foot will catch second wire down and bring it over the top wire, trapping the animal upside down where again, a slow death awaits.
I am not sure of the situation in other parts of the world although I would not be surprised to learn that learn that deer and antelope might suffer similar accidents.
There are awareness programs to address this problem, see an example below.
https://www.lfwseq.org.au/wp-content/uploads/2017/02/Wildlife-Friendly-Fencing-and-Netting.pdf
One solution that I believe would lessen the impact upon wildlife as well as providing a more effective barrier to livestock is to replace barbed wire with 12v electric fences. With solar technology these can be constructed in remote areas and require less material than conventional fencing.
As someone who started working life as a cowboy I can vouch that a determined bovine can usually get through a barbed wire fence with minimal injury. Once they have had a few zaps I find that cattle will studiously avoid electric fences from then on, even when they are deactivated.
In the extremely vast cattle stations of the north and central Australia, electric fences are impossible to maintain due to the sheer length of the perimeter. I see flying foxes and owls regularly dying in them, eg. https://www.inaturalist.org/observations/26046020 Out here, kangaroos are still present, but their densities are lower, and the few that would get caught in a fence would be found by dingoes quickly.
Electric fences here kill chameleons. They are just the right size to bridge the gap.
I can vouch for this. Many years ago I found a dead eastern grey hanging upside down in a barbed wire fence part way up a steep hillside.
Needless to say the smell preceded it by a long distance.
Should the world have fences and other types of walls?
Yes, as others have noted, electric fences pose their own risks, though I don’t know which type of fence causes more mortality - I think it is barbed wire though, for which entanglement is more likely.
Fences also do benefit some organisms (often birds, which can use them for perches), including shrikes, which impale organisms on barbed wire to serve as larders.
There are best practices for fencing (including barbed wire), which can definitely reduce mortality: https://conbio.onlinelibrary.wiley.com/doi/full/10.1111/csp2.285
So educating those installing and maintaining fences and encouraging these practices can make a big impact.
In the western US, there is an amazing amount of barbed wire fencing (I saw an estimate once for the whole US, in miles, but can’t find it right now). Deer, North American elk, and pronghorn can get entangled in it. I’ve been wounded by it multiple times while trying to cross a fenceline and have some scars on my leg as a souvenir. I really hate the stuff.
Also been zapped by an electric cattle fence once while trying to straddle it in a damp meadow. Ouch.
Just for some perspective: in a residential area, I came upon the remains of a cat which had gotten its paw stuck between the planks of a wooden fence. It may have been walking along the top of the fence and tried to jump down, because the stuck paw was considerably higher than it would have been lifted when walking on the ground.
Are there any truly safe fences?
Sage grouse tend to fly into wire fences, especially when startled by a vehicle. Several ranches south of here have added white plastic clips to the top wire along roads to make it more visible and reduce strikes.
We have a palisade fence. Keeps most of the 2 legged antisocials (and dogs) out. Our cats can slip thru when they want to. Birds perch on the rail. Frogs and lizards walk below the bottom rail. Porcupine can dig on our pavement garden.
Many years ago while doing bird field work I came across a bleating White-tailed Deer fawn whose leg was trapped between two taut crossing wires of a (non-electric) fence it had tried to jump. The fawn was very weak and its flesh was already infested with maggots. I was able to extract it and I carried it over my shoulders to a nearby house. The homeowner called the state Department of Natural Resources who gave him permission to shoot it to put it out of its misery.
Also fences play a role in nature conservation, e.g. excluding livestock from sensitive habitats and keeping feral wildlife from entering reserves.
A few years ago when a local conservation agency warden was expecting a critical visit from butterfly ecologists, he strung an electric fence across the entrance gate. By the time the visitors arrived there was a dead buzzard by the gate. It had presumably landed, made a contact between the electric fence and the metal gate and got electrocuted.
A couple of times I have found crows that have been deliberately impaled on barbed wire fences by their wings and left to die. I don’t know whether there is any reason behind it other than cruelty.
Are you sure they were deliberately impaled while alive? I know that in the past people would shoots crows, eagles and other animals then hang the bodies on fences either to display them as trophies or to try and scare away individuals of the same species. I guess if they were in a localised area, it could be the work of a single individual with obvious mental health issues who goes to the effort of catching live crows and killing them in this inhumane manner.
I’ve got a photo of a dead coyote hung on a barbed wire fence in cattle country in rural New Mexico. Presumably a warning to other coyotes. I haven’t posted that on iNat.
That’s interesting to me. In Germany there are electric fences to keep cattle in, but the shock isn’t strong enough to electrocute one, just unpleasant (my guess is 15 kV pulses of less than a millisecond once per second to avoid dangerous energies). And the wires of the fence are all connected, they just have a voltage against earth, so small animals climbing on the fence should be safe. The bottom wire is far enough from the ground that small animals can walk under it (that’s good enough as long as a cow doesn’t fit below).
Things might change with the increasing number of wolves.
Barbed wire in civilian applications illegal as far as I know unless it is on top of a fence three meters high or so in order to protect pedestrians. With no flying foxes or roos, this should be safe for mammals. I haven’t heard of birds getting trapped in barbed wire, but I guess it happens.
Whereas in the Dominican Republic, sometimes the wire holding the gate shut is barbed wire, because they used the wire they had on hand.
I found a (live) domestic cat impaled by the leg on a palisade fence, so it can happen. And the less said about razor wire the better.
Perhaps our fleur-de-lys spikes are less vicious. Our cats can walk along that rail.
Not to mention all the old abandoned fences, where the posts have rotted away and now it’s just miles of rusty barbed wire on the ground waiting to trip you. I’ve gotten tripped and gouged by it more times than I can count. Makes me very glad for tetanus vaccines!