Design and numerical optimisation of a modular crocodile transport unit with leaf-spring vibration isolation for remote terrain

Transporting large saltwater crocodiles over remote, uneven terrain is a specialised wildlife-management operation in which road-induced vibration may contribute to animal stress, fatigue, and injury. Existing modular crocodile transport boxes are robust and field practical, but they typically rely on trailer suspension alone and lack an animal-centred vibration-isolation interface. This study develops and numerically evaluates a passive leaf-spring isolation platform for a modular crocodile transport unit. A baseline two-degree-of-freedom vertical dynamics model was formulated for the coupled trailer-transport-box-animal system under harmonic road-base excitation. An upgraded three-degree-of-freedom model was then introduced by adding a passive suspension stage between the trailer and transport unit, with stiffness and damping selected through parametric dynamic-response analysis. Finite element simulations were used to compare transient deformation and stress transfer in the baseline and isolated configurations. The proposed isolation stage reduced vibration transmission in the low- to mid-frequency range relevant to corrugated and uneven remote roads. Under representative severe excitation cases, finite element results showed approximately 50–75% reductions in peak crocodile-body stress, with comparable reductions in transport-box deformation and structural stress under critical low-frequency conditions. The results indicate that a passive, trailer-mountable isolation platform can improve the mechanical transport environment for large crocodiles while preserving field robustness and operational practicality. The study provides a numerical framework for animal-centred vibration-isolation design and a basis for future field validation using instrumented transport trials and welfare indicators.