most motion sensors of the type used with smartthings are PIR: passive infrared. They detect small changes in heat passing across the sensor.
Although there are some that are described as “pet immune“ that’s just a marketing phrase. They work exactly the same way, you just set the sensitivity higher, in the hopes that it will then only detect the amount of heat given off by a much larger human body.
The problem is that many small animals have resting body temperatures which are higher than humans to begin with, and if they’re jumping and running and active it will go a little bit higher yet, so finding the right adjustment gets really tricky.
Instead, most people try to narrow the detection zone by putting a little pipe over the lens and then aiming it at a height about 4 feet above the ground, so that it will catch a human walking past, but not an animal low on the ground.
Whether that will work in your location or not depends on a lot of things, like how many trees there are. But it’s usually worth a try.
Here’s just one example of what a community member did that worked well for them, but there are lots of variations. Some people also use tape over the lens, although that’s typically less effective.
Alternatively, if you do have serious security concerns (although then I wouldn’t be using SmartThings anyway, but that’s a different discussion) Definitely the best solution to this problem is to use a security camera instead. These will analyze the images and can indeed tell the difference between people and animals. There are lots of different ones available now at different prices and with different integration options, but it’s an approach to look into if you can afford it.
Eventually, MMwave sensors should be able to distinguish between humans and animals, but I don’t believe there are as yet any available that work with SmartThings that have that ability. Aqara has said they intend to add it to their FP2 in the future, but it’s not here yet.
