The motion sensor is seeing the "Light" coming off the "animal" Even us HU-Mans Glow LOL The PIR sensors [Passive Infrared] sees the Glow from the animal, and the hotter something is makes a big different in distant that the PIR can see [think about the difference between a sparrow & a bear]
Also, the PIR sort of uses a Morse Code SOS, it's seeing DOTs of light. Looking into the PIR Lens you can see a bunch of small squares, they are individual small lenses. When an animal is walking along, the Little Lenses are like ON-Off lights to the sensor.[SOS] The sensor only tells the camera to come on when it sees several Dots, trying to ignore false & not take pictures
The Motion Camera has 2 or 3 timers in it. One is to wait the camera to Boot before taking the camera. I think cold makes the Boot longer [90 or 0 degrees] maybe a few seconds If it's a Video, the second is how long a video stays on [camera setting]. The last is when to Wait before being Alarmed. Your settings of the Movement Camera might be 30 seconds or a minute etc before becoming alarmed
That Boot time can make a difference between alarm times. If it's slow, the animal may be in the middle of the picture or even when it's leaving. I sure like when it gets into it.
because of the times, we need to make the animal across the camera, not coming into it or leaving away from it. We want a bunch os Dots, 1 or 2 make the sensor thing its a false, etc
The Night camera Flood Light; those that have lights we can't see, they don't get the distanse of those that we can see like a lot of red cigarettes
Anyway - just adding my 2¢