Marsh helmeted terrapins (Pelomedusa subrufa) potentially facilitate zoochory of fairy shrimp dormant eggs between temporary wetland environments. Dominance hierarchies are known to establish in freshwater testudine populations, with larger-sized or older individuals being dominant over smaller or younger individuals. We assessed for zoochory potential between large- and small-sized turtles by assessing P. subrufa faecal samples from a temporary pan which was observed to hold high densities of both the terrapin and fairy shrimp. Small-sized terrapin dry faecal mass was similar to large-sized terrapin dry faecal mass. However, potential egg densities were much higher in small-sized terrapin. 

We opportunistically tested for the potential of size-related dominance hierarchy in P. subrufa to contribute to dispersal of large branchiopod dormant eggs in a southern African temporary wetland complex. On 12 January 2022, while sampling a wetland site as part of a larger investigation of temporary pan ecology, it was evident that high numbers of testudines were present. Dozens of P. subrufa were seen breaching the water surface with their heads at any one time. Sampling of the pan also revealed high densities of fairy shrimp. As such, we collected terrapins of two discrete size classes (small and large) and obtained faecal samples to assess for the presence of large branchiopod dormant eggs, their viability through hatching experiments, and size-related differences in zoochorous potential. 

A total of 61 terrapins were sampled from the single seine net haul, all identified as P. subrufa. Two size classes were evident, with 36 individuals categorized as small (65 mm–115 mm carapace length) and 25 individuals (190 mm–220 mm carapace length) as large. No P. subrufa individuals between 115 mm and 190 mm were sampled, suggesting that the two size classes represented discrete age groups. It was observed that while taking size measurements upon handling, some P. subrufa would defaecate. The faeces were carefully and opportunistically collected by placing a clean, inverted ziplock bag under the cloaca to catch the defaecant as it was extruded, being careful not to allow contact with any sediment or the animal’s body. Each individual was held for no longer than 60 seconds before being gently released back into the wetland. Faecal matter was attained from 14 individuals in total: 8 individuals of the smaller size class and 6 individuals of the larger size class. Ziplock bags with faecal samples were then placed in a large polystyrene cooling container and allowed to air dry for 7 days prior to laboratory processing.

The dried faecal samples were gently crushed in the Ziplock bags, with the contents then gently transferred into a weighing boat and weighed to the nearest 0.1 mg, using an Ohaus Adventurer Balance, model AR2140. Samples were then carefully transferred to a zooplankton counting tray for processing using a dissecting microscope (Olympus SZ61) at 20 × magnification to assess for potential dormant eggs. Items with external morphological features that looked like dormant eggs were counted and expressed as the density of items per unit dry faecal mass. 

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