with whom RABINO WITZ, Justice, joins, dissenting.
I disagree with what appears to be a requirement that the trial court expressly link the substantial change of circumstances — Elizabeth’s move from Anchorage to the state of Washington — to a negative effect on Derek. In my view, once there is a substantial change of circumstances, the function of the trial court on a motion to change custody is to make a custody award which, under all the circumstances, is in the best interests of the child. We stated as much in House v. House, 779 P.2d 1204 (Alaska 1989):
A court will modify an existing custody arrangement only when “a substantial change in circumstances requires the modification of the award and the modification is in the best interests of the child.” AS 25.20.110....
When the child has been on a relatively stable custody-visitation schedule for a period of time and the primary custodial parent decides to leave the state, the child is faced with a potentially disturbing and upsetting change in circumstances. The child is likely to have less frequent contact with the non-custodial parent who continues to reside in the state. Existing visitation arrangements assume that the parents will continue to live in the same geographic area, and thus will require modification and change when *1365distances increase between the child and the non-custodial parent.
The purpose of maintaining stability in custody arrangements is thus defeated by the custodial parent’s decision to leave Alaska. We therefore hold that the custodial parent’s decision to leave the state with the children constitutes a substantial change in circumstances. If the parents cannot agree on a mutually-acceptable custody and visitation arrangement, the non-custodial parent is entitled to a judicial hearing to resolve whether the best interests of the child require a change in the existing custody or visitation order....
[The non-custodial parent] need only show a change in circumstances before being entitled to a hearing on the children’s best interests.
Id. at 1207-1208 (footnotes and citations omitted).
The error of the majority opinion in this case is in running together the separate requirements of changed circumstances and best interests of the child. The majority opinion states: “At such a hearing, the burden is on the non-custodial parent to demonstrate that the changed circumstances, considered in conjunction with other relevant facts bearing upon the child’s best interests, warrant modification of the custody decree.” See supra. The applicable statute, AS 25.20.110, clearly separates the requirements of changed circumstances and best interests with the word “and”. The statute states in relevant part:
An award of custody of a child or visitation with the child may be modified if the court determines that a change in circumstances requires the modification of the award and the modification is in the best interest of the child. (Emphasis added.)
We recently emphasized the distinct nature of the requirements in Nichols v. Mandolin, 790 P.2d 1367 (Alaska 1990):
These authorities indicate that for a modification of custody to be justified, two circumstances must correspond: (1) the non-custodial parent must bear the burden in the modification proceeding of establishing that a change of circumstances has occurred, and (2) the modification must be in the best interests of the child.
Id. at 1372 (footnotes omitted). In Nichols the change of circumstance was a change in the habits of the non-custodial mother from that of an out-of-control substance abuser to a follower of an abstemious lifestyle. This change obviously did not negatively affect the child or the existing custodial arrangement with the father. Nonetheless, we held that it was sufficient to warrant the best-interests inquiry. Id. at 1372.
Since it is clear in this case that there was a substantial change in circumstances, the question was whether custody with the mother, or with the father, was in the best interests of the child. Judge Carlson recognized this1 and found that the father was the more fit of the two parents to exercise custody. In my view, for the reasons that follow, this finding is not clearly erroneous.
In S.N.E. v. R.L.B., 699 P.2d 875, 878 (Alaska 1985), we stated, “[t]rial courts are vested with broad discretion in child custody determinations. The question upon review is whether the ‘record shows an abuse of discretion or if controlling factual findings are clearly erroneous.’ ” (Citation omitted.) Also, because this case involved presentation of conflicting evidence, it should be remembered that “[i]t is the trial court’s function, and not that of the reviewing court, to judge the credibility of the witnesses and to weigh conflicting evidence .... This is especially true where the trial court’s decision depends largely upon oral testimony.” Penn v. Ivey, 615 P.2d 1, 3 (Alaska 1980) (citations omitted). See also Civil Rule 52(a) (“Findings of fact shall not be set aside unless clearly erroneous, and due regard shall be given to the opportunity of the trial court to judge the credibility of the witnesses.”).
*1366Judge Carlson found that Elizabeth interfered with Geral’s and Derek’s father-son relationship, and that Geral was more likely to promote a healthy relationship between Elizabeth and Derek. In making this finding, Judge Carlson relied on an incident of disagreement between Elizabeth and Geral which resulted in Elizabeth’s refusal to permit visitation and was thus “symptomatic” of their problems. Additionally, four witnesses testified to several other instances in which Elizabeth denied Geral visitation.
In making the finding that Elizabeth interfered with Geral’s and Derek’s relationship, Judge Carlson also relied on evidence that Elizabeth made “disparaging remarks” about Geral and other family members in Derek’s presence. Frank Cox, Derek’s grandfather, testified that at a family gathering Elizabeth “grabbed Derek and start[ed] out the door with him ... she turn[ed] to me and said, and you’ll never see him again, you [expletive deleted].... ”
Judge Carlson made the following finding with respect to Frank Cox’s testimony: “I also believe Frank Cox and his statement and it seemed consistent with other statements which have been made.” (Emphasis added.) Consistent with the testimony of Frank Cox was that of Geral Cox, who testified that, in front of Derek, Elizabeth told him “you’re history, [expletive deleted].”2 Also consistent with Frank Cox’s testimony was that of Sherry Fenton, Geral’s sister, who testified: “I have been on the receiving end of telephone calls [with Elizabeth] where [Geral] is being badmouthed and I can hear Derek ... playing in the background....”
Moreover, there is other evidence which, if believed, lends additional support to Judge Carlson’s finding that Elizabeth interfered with Geral’s and Derek’s father-son relationship. Geral testified that during his visits with Derek, Elizabeth would often call on the telephone and as soon as she and Derek finished talking “[Derek] would be crying and upset, very confused and disturbed.... But, right up until the point where the phone call came along, this kid’s happy go lucky....” Geral described one particular call in which he claimed to have overheard Derek say “I love you too, mom” or “I miss you too, mom” thirty times in nineteen minutes.
Mark Rosenbaum, a former friend of Elizabeth, testified that Elizabeth and Derek appeared to share a close relationship, “to the exclusion of the rest of the world.... ” Similarly, Sherry Fenton testified that:
at family gatherings if Derek fell down and was hurt or if he became upset like little kids do, if Geral tried to go and comfort Derek, [Elizabeth] would physically move Geral aside and ... tell him let me do it_ [I]f Geral tried to discipline Derek, ... [Elizabeth] would also interfere in that.
In light of such evidence, it cannot be said that Judge Carlson’s finding that Elizabeth interfered with the father-son relationship was clearly erroneous.
In his best-interest finding, Judge Carlson also stated: “Ms. Lee loses her temper. There is no question that Mr. Geral Cox loses his temper too, but this court finds that he is the more fit parent to have the care and custody of Derek_” The majority characterizes this finding as “neutral at best.” See supra n. 8. I disagree. The clause, “but this court finds that he is the more fit parent,” clearly suggests that Judge Carlson found Elizabeth’s temper to be more problematic than Geral’s.
Again, there is much evidence in the record which, if believed, lends support to this finding. Geral testified that Elizabeth physically attacked him, including one occasion when Elizabeth threw a pair of scissors at him while he was holding Derek, and another occasion when Elizabeth aimed a loaded pistol at his head. When asked if Elizabeth has a “bad temper,” Sherry Fen-ton testified, “[o]h definitely.... [S]he has unleashed it on various members of our ... family.” Similarly, Frank Cox testified *1367about Elizabeth’s propensity to “fly off the handle and start using profanity or demonstrating her temper on some of the other family members.”
In light of such evidence, it cannot be said that Judge Carlson’s findings with respect to Elizabeth’s fitness as a parent and her interference with the father-son relationship were clearly erroneous. To be sure, Elizabeth attempted to rebut much of this evidence. The question of credibility, however, and the weight to be given the evidence was for Judge Carlson, the trier of fact, and should be deferred to by this court. In this regard, Judge Carlson’s findings make it clear that he was less persuaded by Elizabeth’s evidence than other conflicting evidence. For example, Judge Carlson stated that he “believe[d] Mr. Rosenbaum concerning a diamond ring which [Elizabeth] claimed he gave her and which he claimed was intended for his fiancee.... ” Judge Carlson also “believe[d] Mr. Frank Cox and his statement regarding derogatory remarks and it seemed consistent with other statements made that Ms. Lee loses her temper.”
The trial court correctly determined that the move to Washington was a substantial change in circumstances sufficient to reopen custody. Once custody was re-examined, the trial court found Elizabeth to be less fit as a parent and changed custody to the father. This finding has evidentiary support and is not clearly erroneous. Accordingly, Judge Carlson’s custody determination should be affirmed.
. Judge Carlson stated: "We have either Washington or Alaska, either the mother or the father. That is the state of this record.”
. Geral also testified that, on many occasions, Elizabeth threatened to prevent Geral from seeing Derek, and that these threats upset Derek.