This paper provides a rigorous examination of female reproductive parameters across the lifespan in 2 long-lived primate species. These species are not represented by the comparative primate demography datasets available and have some interesting characteristics that distinguish them from those that are. The paper is very well written, the datasets are large, and the demographic analyses are of the highest standard. I understand these to be sufficient criteria to merit publication in RSOS.

While these are basic data, the authors have provided a sound basis in theory, where relevant, without overreaching. While the results are species-specific, the approach can and should set a standard for other studies. A particular innovation is that the paper carefully dissects the different contributions that factor into reproductive aging patterns. Finally, in terms of impact, these are species that are generating a significant amount of high impact research in other domains, so having foundational life history data to draw from enhances the interpretability of those other studies. This paper will earn many citations.

I have little to critique. Figure 3 is a lot to process. A basic plot of the completed IBIs by age would be more interpretable for most readers, perhaps with the effects plots embedded in the corner. I think it's a reasonable approach since the data indicate that the censored 'open' IBIs are not deviating in a meaningful way from the completed intervals. I'm also curious whether this is really a quadratic aging effect or a more discrete primiparity effect followed by linear aging. Such a figure would also be useful in comparison to the original ASFR curves to get a more holistic grasp of how rates of infant mortality warp the reproductive profile, as they authors suggest they should.

On this note, where you say that high rates of infanticide may obscure the signal of reproductive senescence, it would be helpful to briefly state the reasons why. For example, for some readers, it will be counterintuitive that high mortality drives up the age-specific fertility rate. However, for some primate populations, high mortality leads to unobserved births, so please indicate whether that is (un)likely for either of these. Finally, I was surprised that the paper did not address the fetal loss effects that have been documented in geladas. I am not sure these effects could be approximated in these analyses, and I'm not suggesting that the authors must do so, but I would enjoy some discussion of whether any age trends in these phenomena might contribute in a meaningful way to the observed patterns (especially the species differences).

Please also consider adding the published P. anubis comparator to Figure 1 to help readers see how these populations compared to one that has lower rates of infanticide. .