If you wish to follow the procedure I use as noted earlier this is MY way of doing it, i.e. it works for me, it can be done a million other ways, but follow and you'll see some advantages here:
First create a directory called "sandbox" off the root, i.e. /sandbox on your hard disk. This will contain all sandbox sites, each time you add one for clients create a sub-directory within, i.e. /sandbox/client1
Inside each client directory add "docroot" so you have, for example:
/sandbox/client1/docroot
/sandbox/client2/docroot
Always create the physical directories first, before going into MAMP PRO.
The load up MAMP Pro (minimum settings suggested):
Server tab -> General -> select MAMP PORTS (Apache=8888, MySQL=8889, SSL=8890) Use these ports to avoid issues with ports is use by your Mac already, also these particular ports are traditionally open in firewalls which is why I don't use 81 as some folks do for Apache, for example.
Hosts tab -> General -> + key bottom left panel to add a site
Server Name = client1.localhost
Disk location = /sandbox/client1/docroot
Add an alias using the + key bottom right panel (as many as you wish, I prefer just one, simple):
client1
The reasons you set aliases are 1) to make a friendly URL when displaying site to a client and 2) if a multisite setup, i.e. multiple domains sharing same docroot and source but different databases and files upload path, etc. Aliases are also good to test sites to ensure they are not domain name dependent, i.e. some developers check domain or host name in source - great until the client changes domain name and the source is no longer valid. Especially useful when editing someone else's site.
Apply, allow MAMP Pro to restart Apache/MySQL
Visit the site vie either of these two URL's:
http://client1.localhost:8888
http://client1:8888
Repeat the same procedure for client2, etc. - i.e. in your case subtistute client1 for "dog" and client2 for "cat" and so on. All your client sites will be neatly organized in /sandbox and access via the server name or alias followed by port and path if present. For example,
http://dog.localhost:8888 or maybe
http://dog:8888/mypath/foobar.php using the alias and path in this example.
Using this method means the
http://client1.localhost:8888 is easily identifiable as a LOCAL domain on your Mac when you have other browser windows open for staging and prod, for example.
Get the idea?
-jim