In situ images are pictures taken without touching or catching the subjects. In some types of wildlife photography, such as the photography of reptiles and amphibians, catching and manipulating the subjects is a common practice. Most of the time this matter means very little harm to the animals as most recover quickly from the stress. However, depending on species, age and time of the season, manipulation can actually harm them and result in high stress levels.
Therefore in general the in situ approach is a more eco-friendly way of photographing wildlife.
I dont always practice this myself, but most of the times when I go out in search of reptiles and amphibians I just take in situ images. They dont turn out in the prefectionistic way, that posed images do, but they show the natural behaviours such as feeding, mating, hunting and basking of the animals and are always the biggest "trophyshots" to me.
My all time favorite snake is the adder (Vipera berus).
In 2019 I was lucky enough to spend a lot of time in the Black Forest in Germany. I was out all day for almost 2 months in spring checking out different habitats and populations. Everytime I went out, I took a simple camera setup with me and mostly took images for recognition of individuals. During that time I had the luck to observe many interesting behaviours of adders such as the first males emerging from hibernation and basking for spermatogenesis, mating attempts and even individuals hanging out in an -1°C snowstorm.
Ever since that time, I return to the Black Forest from time to time to meet some of my scaley friends and check out new and possibly extinct populations.