In other words, if for example an oasis has:
10 rats
7 spiders
5 wolves
5 bears
6 crocodiles
4 elephants
You would need 24 cages to take all 4 elephants, 34 to get all the crocs. The oasis would still have 4 rats and 1 spider.
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Actually, it would only take 32 cages to get all the crocs.
There are only 5 wolves and bears in your example.
4 (passes) * 6 (animal types) = 24 and leaves:
6 rats, 3 spiders, 1 wolf, 1 bear, 2 crocs
The next pass (from left to right) collects 5 animals (29 total cages) and leaves:
5 rats, 2 spiders, 1 croc
The next pass collects 3 animals including the last croc to give a tally of 32.
At that point you have 4 rats and a spider left -- and you'd be much better off using any remaining cages in your inventory on a different oasis at this point.
But it would take 2 more cages to get the last spider, then 3 more to get the remaining rats -- but those are all but worthless.
FYI, the defense values of nature animals:
[TABLE='width: 400, align: left']
[tr]
[TD='align: center']Animal[/TD]
[TD='align: center']Infantry Def[/TD]
[TD='align: center']Cavalry Def[/TD]
[/tr]
[tr]
[td]
Rat
[/td]
[td]
25
[/td]
[td]
20
[/td]
[/tr]
[tr]
[td]
Spider
[/td]
[td]
35
[/td]
[td]
40
[/td]
[/tr]
[tr]
[td]
Snake
[/td]
[td]
40
[/td]
[td]
60
[/td]
[/tr]
[tr]
[td]
Bat
[/td]
[td]
66
[/td]
[td]
50
[/td]
[/tr]
[tr]
[td]
Boar
[/td]
[td]
70
[/td]
[td]
33
[/td]
[/tr]
[tr]
[td]
Wolf
[/td]
[td]
80
[/td]
[td]
70
[/td]
[/tr]
[tr]
[td]
Bear
[/td]
[td]
140
[/td]
[td]
200
[/td]
[/tr]
[tr]
[td]
Crocodile
[/td]
[td]
380
[/td]
[td]
240
[/td]
[/tr]
[tr]
[td]
Tiger
[/td]
[td]
170
[/td]
[td]
250
[/td]
[/tr]
[tr]
[td]
Elephant
[/td]
[td]
440
[/td]
[td]
520
[/td]
[/tr]
[/TABLE]