How big would a giant pig need to be in order to carry a 10-foot tall humanoid on its back?

Question

A book that I'm currently writing called Surge features an enemy faction called the Degenerates that are heavily inspired by the Scythians (Indo-Iranian horse nomads that ruled the Eurasian Steppes and Central Asia from the 10th century BCE to the 3rd century CE) and consists mostly of humans parasitized by a prehistoric endoparasite called Echidna (named after the Dracaena that gave birth to numerous monsters in Greek mythology), which parasitizes and radically alters the entire physiology of a wide variety of organisms from the phylum Chordata.

Parasitized humans are transformed into nocturnal humanoids that are facultative quadrupedals and divided into three distinct subspecies, named after the sons of Hercules and Echidna (all of which were ancestors of the Scythians):

• Agathyrsus (Falhumanus clavapugnus): Physically imposing and immensely strong Degenerates used mostly as shock troops, cataphractii and heavy infantry

• Gelonus (Falhumanus tetrabrachius): Lightly-built and four-armed Degenerates which act as scouts, light infantry and cavalry whose purpose is to advance beyond their own front lines for the intent of harassing enemies from afar

• Scythes (Falhumanus sagittarius): Four-eyed Degenerates that have excellent vision and are deployed as marksmen and mounted riflemen, who engage their targets at long range.

Because they are fighting a losing war against a shadowy multi-national black ops unit called S.W.O.R.D using cutting-edge military technology, the Degenerates are forced to engage in guerrilla and asymmetrical warfare against S.W.O.R.D. One such tactic involves Gelonians and Scythi (acting as mounted riflemen/grenadiers and light/normal cavalry) working together in anti-armour hunter-killer cells commanded by Agathyrsi cataphractii (heavily armored cavalry) for the purpose of ambushing armoured vehicles like armoured personnel carriers, tanks and scout cars, utilizing melee weaponry and firearms outfitted with special attachments and high-calibre armour-piercing ammunition coated in scythicon.

In lieu of horses, the Degenerates use a variety of parasitised animals as mounts and the mounts mostly used by Agathyrsi cataphractii are mutated feral pigs designated Phaea and Agathyrsi ride these things using horned saddles similar to those used by the Sarmatians (Indo-Iranian horse nomads closely related to the Scythians) and leather loops as stirrups.

This leaves me with two problems:

• How big would Phaea need to be in order to carry a fully armoured Agathyrsi cataphract (wearing plate armour or an ankle-length cuirass with parapleuridia made of interlaced narrow plates) sporting heavy weaponry, since Agathyrsi stand around 10 feet tall (3.0 meters) and weigh 272 kilograms (599.66 pounds)?
• What sort of body structure would Phaea need to support the weight of a fully armoured Agathyrsi cataphract?

Answer 1

As a rule of thumb pack animals can carry about 30% of their body weight reliably. This is for purposes of packing however, a battle charger would need speed, and so one would need to have that ratio be even better, maybe 15% to 20% of the animals body weight. Minimum size to be reliably ridden is about 800 kilograms, but for battle purposes I would say the lower size limit would need to be roughly about 1000 kilograms or larger. This is an animal that is going to be bigger than a bull moose.