We simply assumed that Filli is a Siskis because Filli matches the description given in Secrets of Deltora. However neither Jasmine nor any chararacter in the Deltora Quest Series ever states that Filli is truly a Siskis. This means that labeling Filli as Siskis, is still an assumption. There could be more small (grey), furred, highly intelligent creatures in the universe of Deltora, for all we know. It seems unlikely that this is the case but we cannot be completely certain because Doran only described the creatures that roamed Deltora while he was alive. Other creatures could have appeared in Deltora after Doran stopped roaming the land. Approximately 500 - 600 years passed since he had stopped doing so, making the appearance of new, yet unknown creatures in the Deltora plausible.
It seems even more unlikely that Filli is not a Siskis, taking into account all the currently available information.
- Very small and bright eyed
- Furred and grey
- Highly-intelligent, as based on his actions throughout the series
Filli was of course found by Jasmine in the Forests of Silence where he had lived. So the evidence that he is a Siskis seems overwhelming. There is only one issues that is rather odd. It has to do with Jasmine discovering and saving Filli. Jasmine states (in the Forests of Silence) that she found Filli, paralysed by the Wenn. As mentioned in Secrets of Deltora, the Wenn only live in First Wood, indicating that Jasmine found Filli in First Wood. However, according to Doran, Siskis only appear in Mid Wood. That is rather odd. There could be 4 explanations for this:
1 Some Siskis moved to the other woods in the Forests of Silence, allowing the Wenn to capture them as prey.
2 Filli wandered outside his natural habitat (Mid Wood) and accidently ventured into Wenn territory. Subsequently, the Wenn captured him.
3 Some Wenn wandered into Mid Wood for unkown reasons and captured Filli and perhaps other Siskis. This behaviour could be a result of lack of prey in First Wood or another unknown reason.
4 Filli is not a Siskis but another creature entirely because neither Siskis nor the Wenn usually leave their respected territories in the Forest of Silence.
Personally, I do believe Filli is a Siskis but still it remains an assumption. I am interested in other people's thoughts on this topic. Let me know what you think.