Natubico is the username of nature protector Nic. Pleumekers, who started here on '09-10-05
All Natubico images: https://commons.wikimedia.org/wiki/Special:ListFiles/Natubico
This user's images are uploaded here under the "Creative Commons Attribution-Share Alike 3.0 Unported license". This licence says among others:"You must attribute the work in the manner specified by the author or licensor".
The relevant specification by the author in this case is the one as follows:
Users of one or more of these images must quote in a usual way the sentence:
"Image made by nature protector Natubico; www.vivism.info"
In case one wants to use images without having to attribute it in this manner, one can contact the author via: email@example.com.
Alert to other uploaders of images on Commons
As a lawyer this user points out that in case uploaders of images on Commons choose as the licence for their uploaded images the recommended "Creative Commons Attribution-Share Alike 3.0 Unported license", they shouldn't presume that this alone is enough to create an obligation for third party users of their images, to attribute these works to them as the author.
For this licence does create the obligation to "attribute the relevant work to the author in the manner as specified by" the last mentioned, but this at the same time does mean that in case this author doesn't specify the manner in which attribution has to happen, in fact no obligation for the third party user is created, so that in fact the uploading author then releases his image(s) into the public domain.
(See also the following Village pump discussion about this subject: []
See also: User:Natubes 
This category recently was removed for unclear reasons. For now it is replaced here.
(There (still) is a category "Animals in the wild", but "Animals in the wild" is not the same as "Free animals"; for instance a mouse in a loft is a free animal, but not really living in the wild. More or less the same goes for a mite on a plant in a private garden).