Shoulder pets

Shoulder pets, as many people refer to them, are most of the time cute and useful tamed to use at your disposal. The following shoulder pets include:

See here for the full list of shoulder pets.

Utility

Roles

Backpack: All shoulder pets have the advantage of serving as backpacks, since the weight of their inventory is reduced by half for us if we carry one on our shoulder.

Shoulder pets with a lot of weight like Jerboa or Bulbdog are good options for this role.
Sinomacrops is even better for this purpose, making all items inside its inventory weigh half as much, if you have one on your shoulder is like its inventory receive a total weight reduction of 75% for your character.
Vulture is the only creature in general that is impossible to directly put items inside its inventory that it is not Spoiled Meat. However, it is possible to put objects in its inventory if it kill a player or creature with said objects.
Otter is the only creature in general that can hold Artifacts on its inventory, so using it as a backpack during caves exploration is a good idea.
On ARK: Survival Ascended the player can access the inventory of the shoulder pet that he is holding on the shoulder by holding R on PC, making easier to employ the function of backpack for the player.

Combat: Shoulder pets can serve as support in combat.

All shoulder pets with the exception of Ichthyornis and Fjordhawk are able to hit with melee attacks from the shoulder.
- The Hesperornis is a special case, it can attack from the shoulder, but because it can only do damage while swimming on water all its attacks does 0.
Mesopithecus in addition to his melee attacks, it can throw poop to the targets and slow them every few seconds, this effect also negates any king of healing effect from consumables.
Microraptor, Dimorphodon and Vulture are a good options on a PvP fight because they directly damage the rider instead of the mount (In case the creature has a rider).
- In Microraptor case it can stun the rider for 10 seconds.
Ferox is a good option for surprise encounters, just give some Element with you and give it to the Ferox when you need some extra muscles.
Pegomastax could be a rare pick for this purpose, but it can even steal items from other player's inventories from the player's shoulder.

Survival Tools: Some shoulder pets can be used as a survival tool.

Sinomacrops is an excellent option to avoid fall damage by using the parachute mode or take high ground on dangerous situations.
Fjordhawk is a keep inventory tool that gives your loot back after you respawn (Works once every hour).
Light Pets like Bulbdog are extremely useful on Aberration to fight against Nameless and Reaper.
Otter and Ferox provide Hypothermic and Hyperthermic insulation, in the Otter case that protection scales with the Melee Damage stat.
- It is not confirmed that the Melee Damage stat of the Ferox increases the insulation that it provide, but it gives much more than the Otter, at least if we compare them at low levels.

Egg Producers: Thanks to their small size, they can be good Egg producers to make Kibble.

Use Vulture and Featherlight for Basic Kibble.
Use Compy, Dimorphodon, Microraptor, Pegomastax, Glowtail and Sinomacrops for Simple Kibble.
Use Ichthyornis and Fjordhawk for Regular Kibble.
Use Golden Hesperornis Egg from Hesperornis for Extraordinary Kibble (Normal Hesperornis Eggs do not produce kibble).
There are no shoulder pets that provide eggs to make Superior Kibble or Exceptional Kibble.

Harvesters: Some shoulder pets can be used for farm some resources.

Hesperornis harvest Raw Fish Meat from small fishes bodies and females can randomly provide a Hesperornis Egg or on rare occasions an special Golden Hesperornis Egg every 5 fishes. This eggs can be cooked for some Oil or Extraordinary Kibble on the Cooking Pot respectively, also the golden egg can be consumed for an experience boost.
Ichthyornis hunts small fishes for Raw Fish Meat and Raw Prime Fish Meat, or it can hunt small ground creatures like Dodos for Raw Prime Meat.
Otter harvest Raw Fish Meat, Silica Pearls and small quantities of Black Pearls from small fishes.
Mesopithecus and Pegomastax can harvest bushes to collect Berries and Seeds respectively.
Even though the Noglin can only gather resources like a normal carnivore, it can mind control a lot of different kind of creatures for some minutes, so it can be useful to temporaly tame something to farm an specific resource.