Please notice the gradual giving in to not be able to hold back powerful reptiles that seem to be related to alligators etc ! The "arms" seems to be getting weaker and weaker, then a hand is used. Then instead of the hand holding the noes, the noes is on it's own and points to the direction of destruction and works it's way down to where the Martians are living underground (it seems), Alligators go into caverns, caves and possibly that is where they may have ended up where some of the entrances of where the Martians where living and maybe still are!
This is more guessing, but I would think that if you have a civilization living underground for thousands upon thousand of years. They may have lost their resistance to an earth type of existence above ground where bacteria reigns supreme etc.
Please notice how Martians utilize the "shoe" analogy!
The analysis I use for the photos and imagery are not mean't to be exacting, only to get you closer to understanding that there is intelligent life on mars (martians). Many of the rocks you may think are rocks, are in fact highly designed sculptures, mechanical objects etc.
Nasa is trying to leak out anomalous imagery with out of course talking about it public! Though most images have been doctored, Nasa is trying to humbly and quietly nudge us along with out going too public about it vocally. Though it is work and painstaking effort to find objects in the images that have not been altered in some way!