DISCUSSION
Homing behavior. — The experiments conducted in this study confirm the Pancake tortoise to exhibit excellent homing abilities. This was attested by the fact that 69.23% of the radio-tracked tortoises that had been displaced from their original home crevices successfully homed. The successful homing again of the first two already homed tortoises when recaptured and re-translocated to a different compass orientation clears any doubt on the existence of homing in the species. Further, the fascinating scenario whereby two pairs of tortoises, collected from and translocated to crevices opposite in direction, crossed paths each journeying home is an allusion to the genius of the homing ability of the Pancake tortoise.
The homing patterns and trajectories imply a response to some cue(s) which at the present cannot be explained with certainty and therefore need further testing. The supposed response to certain cue(s) is evoked by the observation of some distinct movement patterns whereby homing tortoises that had been displaced from the same crevice tended initially to follow the same or nearing paths, only in some cases diverging when nearing their home crevices. We suppose this observed divergence could be as a result of the existence of a wider home range, a delimited area freely traversed by the individual (tortoise) during its normal activities such as feeding, mating, oviposition (Burt 1943).
A number of hypotheses however have been put forward for the mechanisms that make homing possible in animals. Painter and Plachocka (2019) inferring from Mouritsen (2018) and Putman (2018) suggest that for animals to achieve migration, they detect various cues to formulate a map and compass, with the map providing position relative to a target and the compass giving a heading. Such cues include geomagnetic field responses (Brothers and Lohmann 2015), odour plumes (Koch et al. 1969) and celestial bodies (sun, moon) (Foster et al. 2018).
Even though homing has only been investigated in a few tortoise species, the use of such cues certainly has been documented. Chelazzi and Delfino (1986) state that the Herman’s tortoise (Tesudo hermanni ) makes use of olfaction during homing. Cannor (1996) records that vision and olfaction appear to be important senses for the orientation and movements of Gopher tortoises. Gourley (1974) also records that the Gopher tortoise (Gopherus Polyphemus ) is capable of making use of sun compass orientation, albeit secondarily to visual landmarks (Cannor 1996). In Pancake tortoise it appears that the response to whichever cue(s) is more perfected in adults than juveniles although it was only one juvenile that was tested. Also, despite our study not investigating further on the cues utilized during the homing, we nonetheless feel that since our tortoises were translocated in closed boxes, the use of visual landmarks by the species may play a lesser role when homing.
Although traveling in incomparable medium with tortoises, Gould (2015) states that Sea turtles memorize the magnetic coordinates of their natal beach, returning to that combination of parameters to lay eggs decades later. To accomplish this feat, Gould (2015) reiterates that the young animal is hypothesized to ‘imprint’ on the nest site, storing navigational information for later use. Lohmann et al (2001, 2004) explain the global cues used during the homing of Loggerhead sea turtles, as well as juvenile orientation to the initial feeding area, to be unambiguously magnetic.
Site fidelity. — The successful homing of the displaced Pancake tortoises over vast and heterogeneous landscapes is indisputable proof of strong site fidelity in the species. The explanation for the results showing a significantly decreasing trend (Mann-Kendall) is that there were translocations into stations 1, 2 and 4 and consequently the decreasing trend is attributable to the homing movement out of the crevices. Also occasional tortoise dispersals from station 3 to station 4 and back is assumed to have led to decreasing trends in both the stations. The reason as to why there was no statistically significant trend in station 6 despite tortoises having been removed from there is that the tortoises homed within a period (3-5 days) short for a trend to be detected in the long term. ‘No trend’ in the other stations implied that since there were no translocations out of them, the tortoises initially present remained in the crevices throughout the study period. Considering that reproduction rate in the species is low (Spawls et al. 2002; Schmidt 2006; Mwaya et al. 2018), and our observations that the few hatchlings/juveniles which are reprod uced always find refuge farther away from the adult tortoise crevices, the tortoise numbers in the short term were unlikely to increase hence the constant number in the crevices over the study duration. Our results ultimately show that the tortoises always abided by their crevices and if displaced returned home alluding to strong site fidelity.
These findings agree with Malonza (2003), Wood and MacKay (1997) and Moll and Klemens (1996) who also documented that the Pancake tortoise resides in well-defined home ranges over long periods of time. We believe that such fidelity to the specific crevice and associated habitats certainly confers special survival advantages to the species. For instance, as animals become familiar with a site, site fidelity can help them know where to find good food, nesting sites as well as help them avoid predators (Merkle et al. 2022).
Territoriality. — The camera trap events and ad libitum observations that showed events of aggressive behavior with resident males fighting and chasing away other visiting males add to our knowledge, not only of site fidelity, but also of territoriality. A study by Wood and MacKay (1997) notes that adult males and females of Pancake tortoises may be territorial with respect to other members of their own sex but not to members of the opposite gender. Their observation, further showed that a male may exclude all the other males and a female may do likewise with all other mature females. Our study however did not observe females fighting other females as up to five females were found residing in the same crevice harmoniously for over two years. Since the general habitats surrounding the crevices seem to have comparable vegetation structure and composition, mate territorialism becomes the only reasonable candidate for the aggressive behavior observed.