It's about nine-tenths as heavy as an Elephant.
In other words, 135 firkins is 0.910 times the weight of an Elephant, and the weight of an Elephant is 1.10 times that amount.(for African bush elephant, Loxodonta africana) (Adult, bull)
A bull African bush elephant weighs about 150 firkins. Among African elephants, both males and females have tusks (whereas female Asian elephants, Elephas maximus, do not have tusks) which can grow to 3 m (10 ft) and weigh up to 2.20 firkins.
It's about nine-tenths as heavy as a Tyrannosaurus rex.
In other words, 135 firkins is 0.860 times the weight of a Tyrannosaurus rex, and the weight of a Tyrannosaurus rex is 1.20 times that amount.(for FMNH PR2081, a.k.a. "Sue") (a.k.a. Tyrannosaurus, a.k.a. T-Rex) (estimated live weight)
The notable Tyrannosaurus specimen housed at the Field Museum of Natural History in Chicago, Illinois, "Sue," is estimated to have weighed about 160 firkins while alive. A renowned predator in popular culture, the teeth of tyrannosaurus rex were up to 33.02 cm (13 in) long.
It's about one-and-a-half times as heavy as a Hippopotamus.
In other words, 135 firkins is 1.470 times the weight of a Hippopotamus, and the weight of a Hippopotamus is 0.680 times that amount.(Hippopotamus amphibius) (adult, male)
The average weight of an adult male hippopotamus ranges from 91.90 firkins. Appearances to the contrary, adult hippos cannot swim or float in water; they actually move by leaping and walking across lake bottoms at about 8 kph (5 mph).
It's about two times as heavy as The Tongue of a Blue Whale.
In other words, the weight of The Tongue of a Blue Whale is 0.50 times 135 firkins.(Balaenoptera musculus) (adult)
The tongue of a Blue Whale can weigh up to 66 firkins. Despite their tremendous size, blue whales feed almost exclusively on tiny crustaceans called krill and cannot swallow anything much larger than a beach ball.
It's about half as heavy as an Anchor of a Cruise Ship.
In other words, 135 firkins is 0.4880 times the weight of an Anchor of a Cruise Ship, and the weight of an Anchor of a Cruise Ship is 2.05 times that amount.(for QE2 forward anchor, a.k.a. RMS Queen Elizabeth 2)
Each of the forward anchors of the RMS Queen Elizabeth 2 weighs 277 firkins. The anchor of the QE2 now sits in front of the Holyrood Church in Southampton, England, United Kingdom, along a pedestrian tourist route known as "the QE2 mile."
It's about two times as heavy as a Giraffe.
In other words, 135 firkins is 2.20 times the weight of a Giraffe, and the weight of a Giraffe is 0.450 times that amount.(Giraffa camelopardalis reticulata) (adult, male)
An adult, male giraffe weighs an average of 61 firkins. Reaching 5.5 m (18 ft) in height by adulthood, giraffe calves can grow as much as 3 cm (1 in) per day.
It's about two-and-a-half times as heavy as a Rhinoceros.
In other words, the weight of a Rhinoceros is 0.380 times 135 firkins.(for Black rhinoceros, Diceros bicornis) (Adult, male)
An adult black rhinoceros weighs between 51 firkins. Rhinoceros are extremely aggressive — nearly one of every two males will die as a result of fighting with other rhinoceros.